Main shaft device and machine tool with the same

ABSTRACT

A machine tool including a bed; a work table horizontally movable on the bed; a column extending from the bed; a spindle head movable on the column; an outer cylinder attached inside the spindle head; a stator of a built-in motor; and a spindle sub-cartridge. The spindle sub-cartridge includes a vertical rotating shaft; a front side bearing having an inner ring fitted to a front end of the rotating shaft and an outer ring fitted to a front housing; a rotor of the built-in motor; a rear side bearing having an inner ring fitted to a rear end of the rotating shaft and an outer ring fitted to a bearing sleeve. The movable range of the spindle head in the vertical direction is longer than a length necessary for inserting the spindle sub-cartridge into the spindle head. The spindle sub-cartridge is can be disassembled and assembled integrally with respect to the spindle head.

This is a divisional of application Ser. No. 10/534,354 filed May 9,2005, now U.S. Pat. No. 7,311,482, which was the national stage ofInternational Application No. PCT/JP2004/004591, filed Mar. 31, 2004,which claims priority from Japanese Patent Application Nos. 2003-096503filed on Mar. 31, 2003, 2003-103219 filed on Apr. 7, 2003, 2003-384703filed on Nov. 14, 2003, 2003-419854 filed on Dec. 17, 2003 and2004-000261 filed Jan. 5, 2004, the disclosures of which areincorporated in their entirety.

TECHNICAL FIELD

The present invention relates to a spindle apparatus equipped in amachine tool such as a milling machine or a machining center, and amachine tool having the spindle apparatus.

BACKGROUND ART

Conventionally, as a spindle apparatus of a machine tool or the like, abuilt-in motor spindle apparatus having a front side bearing interposedbetween a front housing and a spindle shaft and a rear side bearinginterposed on an outer periphery of a rear portion of the spindle shaftis conventionally known, as described in, for example, JP-A-7-112303(hereafter referred to as a “patent document 1”) and JP-A-2003-159622(hereafter referred to as a “patent document 2”).

As shown in FIG. 31, a built-in motor spindle apparatus 500 disclosed inthe patent documents 1 and 2 includes a motor housing 502 held by a unitsupporting member 501, as well as a front housing 503 which is joined toa front side of this motor housing 502. The built-in motor spindleapparatus 500 further includes a spindle shaft 505, which is fitted inthis motor housing 502 and the front housing 503, and a stator 506secured to an inner periphery of an intermediate portion of the motorhousing 502, a rotor 507 being secured to an outer periphery of theintermediate portion of the motor housing 502.

Further, the spindle shaft 505 is formed in a hollow tubular shape, anda drawbar 509 which is urged by a coned disk spring 508 and is slidablein the tube is provided in the tube, a chuck portion 510 being providedat its tip. Further, four front side bearings 511 are interposed betweenthe front housing 503 and the spindle shaft 505. In addition, a rearside bearing 512, which is a cylindrical roller bearing, and a bearingsleeve 513 are fitted over an outer periphery of a rear portion of thespindle shaft 505, and a rear cover 514 is bolted to a rear portion ofthe motor housing 502.

Incidentally, with the machine tool, a failure of the spindle isfrequently caused primarily by damage occurring in the bearings. Itscauses are the life of the bearings, a collision of the spindle due to amachining program error, and the like. The reduction of the time(downtime) from the failure of the spindle until it is reset isparticularly important at a site of parts machining which is directlylinked to a production line of automotive parts machining or the like.In addition, a trend toward the higher speed of the machine tool spindleis under way, and the spindle bearing life for low-speed machines (lessthan 600,000 dmN) (dm: pitch circle diameter (mm) of a rolling bearing,N: rotational speed (min⁻¹)) has been virtually unlimited at 100,000hours or more, whereas the spindle bearing life for high-speed machinesis becoming 10,000 to 20,000 hours. Thus, the spindle bearings have cometo be regarded as being handled as consumables, so that there has arisena need to lower the maintenance cost.

With the spindle apparatus 500 disclosed in the above-described patentdocument 1, the spindle shaft 505 is arranged to be drawn out for theimprovement of the maintenance efficiency. However, with thisarrangement, although the spindle shaft 505 can be drawn out, nodescription is given as to the replacement of the rear side bearing 512which is a cylindrical roller bearing. If the rear side bearing 512 isdamaged, the time and trouble involved in the maintenance remainunchanged from a conventional case. In addition, since a projectingportion of a lubricating nozzle is not provided to draw out the spindleshaft 505, 2 to 10 hours or thereabouts is inevitably required as therunning-in time for the rear side bearing 512 after its assembly. Hence,there has been a problem in that the downtime becomes long.

In addition, with the spindle apparatus 500 disclosed in theabove-described patent document 2, there has been a problem in that theoperating efficiency is poor, since at the time of removing the spindle,an operator must move around to the rear side to remove a pipe, and atthe time of assembly an operation is further required for adjusting abearing case to the phase of the pipe.

As another example of the spindle apparatus of a machine tool or thelike, a spindle apparatus in which a plurality of coned disk springs arestacked and disposed between the sleeve housing and the bearing sleeveis conventionally known, as described in, for example, JP-A-11-138305(hereafter referred to as a “patent document 3”).

In the spindle apparatus, one bearing (rear side bearing) is fixed tothe bearing sleeve which is fitted in the sleeve housing and is movablein the axial direction, so as to be able to absorb the axialdisplacement when the rotating shaft has become axially elongated due toheat generation or the like at the time of high-speed rotation. As forthe fit between the sleeve housing and the bearing sleeve, a planesurface sliding method in which a simple fit is used, a ball slidingmethod using an axially movable ball bush, and the like are known.Slidability as well as radial stiffness and axial vibration dampingproperties are required for the bearing sleeve for supporting the freeend side of the rotating shaft.

In the case where the plane surface sliding method is adopted for thefitting between the sleeve housing and the bearing sleeve, the fittingclearance decreases in conjunction with heat generation, so that it isnecessary to set an initial fitting clearance to be large. This hasconstituted one factor increasing the vibration of the rotating shaftwhen the spindle apparatus rotates. Meanwhile, in the case of the ballsliding method of the fitting using the ball bush, an increase in theinterference due to heat generation hinders the smooth axial movement ofthe bearing sleeve, and the axial stiffness is low. Hence, there havebeen cases where self-excited vibration called the chattering of therotating shaft occurs.

For this reason, in the spindle apparatus disclosed in the patentdocument 3, to damp the self-excited vibration of the rotating shaft,the arrangement is provided such that a plurality of coned disk springsare stacked between the sleeve housing and the bearing sleeve so as toincrease the axial stiffness and prevent the self-excited vibrationthrough the friction of the coned disk springs.

However, in the spindle apparatus disclosed in the patent document 3,the self-excited vibration is arranged to be damped through the frictionof the coned disk springs, and the damping force is determined by thespring constant of the coned disk spring, the number of the coned disksprings, their installation direction, and the like. These items, whichare set at the time of assembling the spindle apparatus, are constantand fixed unless the coned disk springs are recombined by such asdisassembling the spindle apparatus. In other words, it has beendifficult to change the characteristics in correspondence with theconditions of rotation, e.g., to reset the damping factor and the liketo values optimal to the operating conditions.

In recent years, the trend toward the higher speed of the spindleapparatus is noticeable, and the amount of heat generated has alsoincreased in consequence of the trend toward the higher speed.Therefore, there has been a demand for a more sophisticated method ofsupporting the rotating shaft, which is capable of coping with it.

In addition, as one example of the machine tool having the spindleapparatus, a machine tool in which the housing of the spindle head isdivided into a front housing and a rear housing and the two members arefastened by bolts is conventionally known, as described in, for example,JP-A-2003-159622 (the “patent document 2”).

In such a machine tool, an arrangement is provided such that not theentire cartridge but the shaft, the front side bearing, the fronthousing, the rotor of the built-in motor, the rear side bearing, and therear housing are removed as a spindle sub-assembly by leaving the statorof the built-in motor and the outer cylinder.

Incidentally, in a machine tool, in a case where the spindle apparatusis replaced due to a failure or the arrival of its life, with a typewhich is so constructed as to incorporate the bearings and the statorindividually into the spindle head, the replacement operation takestime, and the downtime of the machine increases. Accordingly, it isknown that the replacement time can be shorted by structuring thespindle apparatus so as to be capable of being divided and assembledintegrally as a cartridge with respect to the spindle head.

Although there is also a type having a structure in which the entirespindle cartridge is drawn out, with this structure it is necessary todisengage oil and air pressure pipings and cables in the case of thebuilt-in motor system, so that the operation takes time.

In contrast, in the above-described patent document 2, the arrangementis provided such that not the entire cartridge but the shaft, the frontside bearing, the front housing, the rotor of the built-in motor, therear side bearing, and the rear housing are removed integrally as aspindle sub-assembly by leaving the stator of the built-in motor and theouter cylinder. However, although at the time of disassembling thespindle cartridge it is necessary to withdraw from the spindle head allthe portion of the spindle cartridge which is located inside the spindlehead, the spindle cartridge is a heavy piece and cannot be pulled outmanually.

Accordingly, the spindle cartridge can be drawn out safely and in ashort time if the spindle cartridge is fixed to a worktable of themachine tool and is drawn out by making use of the feeding in a Z-axiswhich is a feeding axis parallel to the axial direction of the spindle.However, if the amount of Z-axis movement is shorter than the lengthnecessary for the spindle cartridge to be completely drawn out from thespindle head, the withdrawal making use of the Z-axis feeding becomesimpossible.

In addition, when the spindle cartridge is disassembled, the operationof disengaging many oil and air pressure pipings and cables is required,and the replacement time is long. In contrast, in the case of thespindle sub-cartridge, the operation of disengaging the many oil and airpressure pipings and cables is not required. However, if the amount ofZ-axis movement is shorter than the length necessary for the spindlecartridge to be completely drawn out from the spindle head, thewithdrawal making use of the Z-axis feeding becomes similarlyimpossible.

Meanwhile, in the case of a structure in which a flat mounting surfaceis provided on a side surface of the spindle cartridge and the spindlecartridge is fixed from its side surface to the spindle head, thespindle cartridge can be disassembled from the spindle head irrespectiveof the amount of Z-axis movement. With this method, however, since theload is received only by the side surface of the spindle cartridge, thefastening stiffness becomes low, so that this method is inappropriate interms of stiffness.

In addition, with the above-described patent document 2, it isunnecessary to disengage the oil and air pressure pipings and cables,but parts cannot be removed excluding those parts which can be removedas a sub-cartridge. For this reason, this arrangement does not functioneffectively at the time of the failure of the stator, an unclampcylinder, or the like, so that this arrangement lacks a functionalfeature concerning disassembly.

The spindle apparatus and the machine tool having the spindle apparatusin accordance with the invention are invented in view of suchcircumstances, and a first object of the invention is to provide aspindle apparatus which facilitates assembling and removing operationsat the time of maintenance and which is low cost. A second object of theinvention is to provide a spindle apparatus which has high stiffness andexcels in satisfactory damping properties and slidability. A thirdobject of the invention is to provide a machine tool in which a spindlecartridge or a spindle sub-cartridge can be disassembled and assembledin a short time, which minimizes the machine height, and which has highstiffness. A fourth object of the invention is to provide a spindleapparatus which is capable of attaining improvement of the maintenanceefficiency by making it possible to facilitate the operation ofreplacing all internal component parts.

DISCLOSURE OF THE INVENTION

The spindle apparatus subject to the invention has an outer cylinder, arotating shaft, a front side bearing, and a rear side bearing in thesame way as the above-described conventional structure, and is assembledto a machine too, and the rotating shaft rotates at high speed.

In particular, the spindle apparatus includes: an outer cylinder havinga stator; a rotatable rotating shaft having a rotor; a front sidebearing having an outer ring fixed to a front housing and an inner ringfitted over one end of the rotating shaft; a bearing sleeve disposed onanother end side of the rotating shaft and fitted in the outer cylinderso as to be movable in an axial direction of the rotating shaft; and arear side bearing having an inner ring fitted over the other end of therotating shaft and an outer ring fixed to the bearing sleeve torotatably support the rotating shaft in cooperation with the front sidebearing, wherein the diameter becomes smaller in the order of an innerperipheral diameter of the outer cylinder, an inside diameter of thestator, and an outside diameter of the bearing sleeve, a sub-assemblymade up of the front housing, the rotating shaft, and the bearing sleeveis withdrawable from the outer cylinder, and a radius of a rotatingparts in an arbitrary section located rearwardly of the bearing sleeveis smaller than a minimum radius of a non-rotating parts between a rearend of the bearing sleeve and the section.

In addition, the spindle apparatus includes: an outer cylinder having astator; a rotatable rotating shaft having a rotor; a front side bearinghaving an outer ring fixed to a front housing and an inner ring fittedover one end of the rotating shaft; a bearing sleeve disposed on anotherend side of the rotating shaft and fitted in the outer cylinder so as tobe movable in an axial direction of the rotating shaft; and a rear sidebearing having an inner ring fitted over the other end of the rotatingshaft and an outer ring fixed to the bearing sleeve to rotatably supportthe rotating shaft in cooperation with the front side bearing, wherein asub-assembly made up of the front housing, the rotating shaft, and thebearing sleeve is withdrawable from the outer cylinder, and an insidediameter part capable of replacing a tool is incorporated in therotating shaft, and a piston mechanism for tool replacement is provided.

In addition, in the spindle apparatus a distance between a mountingreference plane of the sub-assembly and a piston pressing surface of theinside diameter part is adjusted to within ±0.1 mm relative to areference dimension.

In addition, in the spindle apparatus, the inside diameter part isincorporated in such a manner as to be capable of compressing a spring,and an adjustment part is fixed to a rear portion of the inside diameterpart, the piston pressing surface for pressing the piston mechanismbeing formed on the adjustment part.

In addition, in the spindle apparatus, the front housing is fitted tothe outer cylinder with an interference fit.

In addition, in the spindle apparatus, the bearing sleeve is fitted in asleeve housing, and an outside diameter of the bearing sleeve isclearance-fitted with respect to an inside diameter of the sleevehousing.

In addition, in the spindle apparatus, a plurality of pairs of O-ringsare interposed between the outside diameter of the bearing sleeve andthe inside diameter of the sleeve housing.

In addition, in the spindle apparatus, a ratio between, on the one hand,a fitting length of the bearing sleeve and the sleeve housing and, onthe other hand, an outside diameter of the bearing sleeve is set withina range of “fitting length/outside diameter=0.45 to 0.8.”

In addition, in the spindle apparatus, there are provided a plurality oflubricant discharging holes provided circumferentially in the bearingsleeve, circumferential grooves provided in a fitting surface of anouter periphery of the bearing sleeve, and radial lubricant supplyingpassages communicatingly connected to the circumferential grooves.

In addition, in the spindle apparatus, the rear side bearing is aback-to-back arrangement angular contact ball bearing withfixed-position preload.

In addition, in the spindle apparatus, grease lubrication is adopted.

In addition, in the spindle apparatus, a grease replenishing unit isprovided.

In addition, in the spindle apparatus, a mechanism is provided fordischarging excess grease after the supply of grease.

In addition, in spindle apparatus, a very small amount of lubrication ofany one of oil-air, oil-mist, and direct-injection lubrication is used.

In addition, the spindle apparatus includes: a rotatable rotating shafthaving a rotor; a front side bearing having an outer ring fixed to afront housing and an inner ring fitted over one end of the rotatingshaft; a bearing sleeve disposed on another end side of the rotatingshaft and fitted in a sleeve housing so as to be movable in an axialdirection of the rotating shaft; and a rear side bearing having an innerring fitted over the other end of the rotating shaft and an outer ringfixed to the bearing sleeve to rotatably support the rotating shaft incooperation with the front side bearing, the spindle apparatus beingcapable of displacing the other end of the rotating shaft in the axialdirection, wherein an elastic body for sealing the sleeve housing andthe bearing sleeve is provided between fitting surfaces of the sleevehousing and the bearing sleeve, and a fluid for applying pressure isarranged to be supplied to the elastic body.

In addition, in the spindle apparatus, the elastic body is an O-ring,and the fluid is compressed air, the compressed air being suppliedbetween the O-rings provided in a plural number, so as to apply thepressure to the O-rings.

In addition, in the spindle apparatus, the pressure of the fluid forapplying pressure to the elastic body is variable.

In addition, in the spindle apparatus, the O-ring is formed of nitrilerubber or fluoro rubber, and the interference when the O-ring isinstalled between the sleeve housing and the bearing sleeve is not lessthan 10% of a working standard value and not more than the workingstandard value.

In addition, in the spindle apparatus, a plurality of sets of elasticbodies are disposed as the elastic body, each of the sets being formedby a plurality of elastic bodies, one of the sets of elastic bodiesarranged at both ends being disposed on the bearing sleeve, another oneof the sets of elastic bodies being disposed on the sleeve housing.

In addition, a machine tool includes: a spindle cartridge including arotatable rotating shaft, a front side bearing having an inner ringfitted over one end of the rotating shaft, a front housing in which anouter ring of the front side bearing is fitted, a rotor of a built-inmotor, a stator of the built-in motor, a rear side bearing having aninner ring in which a rear end of the rotating shaft is fitted, and anouter cylinder fitted in a spindle head, wherein the spindle cartridgeis inserted in a spindle cartridge gripping portion provided in an axialdirection of the spindle head, and an amount of movement in a feedingaxis direction parallel to an axial direction of the rotating shaft isset to be longer than a length necessary for inserting the spindlecartridge into the spindle head, whereby the spindle cartridge iscapable of being disassembled and assembled integrally with respect tothe spindle head.

In addition, a machine tool includes: a spindle sub-cartridge includinga rotatable rotating shaft, a front side bearing having an inner ringfitted over one end of the rotating shaft, a front housing in which anouter ring of the front side bearing is fitted, a rotor of a built-inmotor, a stator of the built-in motor, a rear side bearing having aninner ring in which a rear end of the rotating shaft is fitted, and abearing sleeve in which an outer ring of the rear side bearing isfitted, wherein an amount of movement in a feeding axis directionparallel to an axial direction of the rotating shaft is set to be longerthan a length necessary for inserting the spindle sub-cartridge into thespindle head, whereby the spindle sub-cartridge is capable of beingdisassembled and assembled integrally with respect to the spindle head.

In addition, in the machine tool, the spindle cartridge gripping portionof the spindle head can be disassembled by being divided at a positionfor dividing at least in half.

In addition, a spindle apparatus includes: an outer cylinder having astator; a spindle head in which the outer cylinder is fitted; arotatable rotating shaft with a rotor disposed inside the stator; afront side bearing having an inner ring in which one end of the rotatingshaft is fitted; a rear side bearing having an inner ring in whichanother end of the rotating shaft is fitted; a front housing in which anouter ring of the front side bearing is fitted and which is installed atone end of the outer cylinder; a sleeve housing in which an outer ringof the rear side bearing is fitted and which is fitted in another end ofthe outer cylinder; and a tool unclamp cylinder fixed to one end of theouter cylinder, wherein the rotating shaft with the rotor, the frontside bearing, the rear side bearing, the front housing, and the sleevehousing are integrally assembled to form a spindle sub-cartridge, thespindle sub-cartridge, the outer cylinder, and the tool unclamp cylinderare arranged in a three-divided form, and the spindle sub-cartridge iswithdrawable from the outer cylinder.

In addition, in the spindle apparatus, the tool unclamp cylinder iswithdrawable from the outer cylinder.

In addition, in the spindle apparatus, an assembly of the tool unclampcylinder and the outer cylinder with the spindle sub-cartridge withdrawntherefrom is withdrawable from the spindle head.

In addition, in the spindle apparatus, an assembly of the spindlesub-cartridge, the outer cylinder, and the tool unclamp cylinder iswithdrawable from the spindle head.

In addition, in the spindle apparatus, a coupler having various fluidpipings and a power supply coupler is detachably installed on the toolunclamp cylinder or the outer cylinder.

In addition, in the spindle apparatus, a sensor for detecting therotation of the rotating shaft is disposed between the rotating shaftand the outer cylinder.

According to the spindle apparatus of the invention constructed asdescribed above, a sub-assembly made up of the front housing, therotating shaft, and the bearing sleeve is withdrawable from the outercylinder. As a result, the assembling efficiency improves, and theseparts can be replaced speedily when they become damaged. In addition, asfor the bearing sleeve, since the rear side bearing is in an assembledstate, the state of grease does not change in the withdrawal andinsertion of the sub-assembly.

Accordingly, with this spindle apparatus, as the sub-assembly is kept instock after performing the running-in operation in advance by usinganother outer cylinder, the sub-assembly can be replaced at the time ofthe damage of the rotating shaft, and the normal operation is madepossible immediately, thereby permitting a substantial reduction indowntime. In addition, a cost reduction is made possible in comparisonwith the replacement of the entire spindle apparatus, and a reduction ininventory cost is also made possible. As a result, it becomes possibleto overcome the conventional problem that the downtime becomes longsince the running-in operation of the bearings is required afterassembly since grease lubrication is adopted for which the time andtrouble in maintenance cannot be reduced.

In addition, the diameter becomes smaller in the order of the innerperipheral diameter of the outer cylinder, the inside diameter of thestator, and the outside diameter of the bearing sleeve. To ensure thatthe non-rotating parts does not constitute a hindrance when an attemptis made to withdraw the spindle in the rear of the bearing sleeve, theradius of the rotating part in an arbitrary section is smaller than aminimum radius of the non-rotating part between the rear end of thebearing sleeve and that section, thereby preventing the non-rotatingpart from constituting a hindrance. Accordingly, when an attempt is madeto withdraw the sub-assembly, the piston mechanism and the like, whichare the non-rotating part, for holding/releasing the tool do notconstitute a hindrance

Here, as the front side bearing, it is possible to cite by way ofexample a multi-row arrangement angular contact ball bearing. Inaddition, as the rear side bearing, it is possible to cite by way ofexample a pair of angular contact ball bearings.

In addition, if the sub-assembly made up of the front housing, therotating shaft, and the bearing sleeve is withdrawable from the outercylinder, the assembling efficiency improves, and these parts can bereplaced speedily when they became damaged. In addition, as for thebearing sleeve, since the rear side bearing is in an assembled state,the state of grease does not change in the withdrawal and insertion ofthe sub-assembly.

Accordingly, with this spindle apparatus, as the sub-assembly is kept instock after performing the running-in operation in advance by usinganother outer cylinder, the sub-assembly can be replaced at the time ofthe damage of the spindle apparatus, and the normal operation is madepossible immediately, thereby permitting a substantial reduction indowntime. In addition, a cost reduction is made possible in comparisonwith the replacement of the entire spindle apparatus, and a reduction ininventory cost is also made possible.

In addition, since the tool replacement is effected through the pistonmechanism by the inside diameter part incorporated in the rotatingshaft, in comparison with an externally exposed type, it is possible toeffect the tool replacement with high lubricating performance.

In addition, unclamping can be performed appropriately if the distancebetween the mounting reference plane of the sub-assembly and the pistonpressing surface of the inside diameter part is adjusted to within ±0.1mm relative to the reference dimension. Therefore, piston adjustment ismade unnecessary at the time of performing the replacement of thesub-assembly, making it possible to improve the maintenance efficiency.

In addition, if the inside diameter part is incorporated in such amanner as to be capable of compressing a spring, and the adjustment partis fixed to a rear portion of the inside diameter part, and the pistonpressing surface for pressing the piston mechanism is formed on theadjustment part, then the amount of pushing of the tool holder can beset to a predetermined value by the adjustment part. Therefore, it ispossible to appropriately effect unclamping by adjusting its tolerance.As a result, piston adjustment is made unnecessary at the time ofperforming replacement of the inside diameter part, making it possibleto improve the maintenance efficiency.

In addition, if the front housing is fitted to the outer cylinder withan interference fit, in cases such as where the sub-assembly issubjected to disassembly, assembly, or replacement, offset does notoccur between the axes of the front housing and the outer cylinder,making it possible to maintain high accuracy.

In addition, if the bearing sleeve is fitted in the sleeve housing, andthe outside diameter of the bearing sleeve is clearance-fitted withrespect to the inside diameter of the sleeve housing, the rear sidebearing and the bearing sleeve function mainly to support the rotatingshaft, but are capable of absorbing with a simple structure the axialdisplacement such as thermal expansion due to the heat generation by therotor.

In addition, if a plurality of pairs of O-rings are interposed betweenthe outside diameter of the bearing sleeve and the inside diameter ofthe sleeve housing, the leakage of the lubricant is prevented by theplurality of pairs of O-rings between the outside diameter of thebearing sleeve and the inside diameter of the sleeve housing, and thevibration of the bearing sleeve can be damped by the damping effectbased on the interference of the O-rings.

In addition, if the ratio between, on the one hand, a fitting length ofthe bearing sleeve and the sleeve housing and, on the other hand, theoutside diameter of the bearing sleeve is set within a range of “fittinglength/outside diameter=0.45 to 0.8,” the outside diameter of thebearing sleeve and the length of the fitting portion of the sleevehousing is set to an appropriate relationship. Hence, it is possible toobtain a structure of the sub-assembly excelling in the maintenanceefficiency and the performance of the machine tool.

In addition, if there are provided a plurality of lubricant dischargingholes provided circumferentially in the bearing sleeve, circumferentialgrooves provided in a fitting surface of the outer periphery of thebearing sleeve, and radial lubricant supplying passages communicatinglyconnected to the circumferential grooves, then it becomes possible todischarge the lubricant without a problem at whatever phase the bearingsleeve may be. Although a discharging hole is required on the lower sidein the case of, for instance, a horizontally mounted spindle,discharging can be effected since one of the holes faces the lower side.Furthermore, the lubricant can be supplied at whatever position thebearing sleeve may be. Accordingly, it becomes unnecessary to adjust thephase of the bearing sleeve, so that the operating efficiency inmaintenance is excellent.

In addition, if the rear side bearing is a back-to-back arrangementangular contact ball bearing with fixed-position preload, it is possibleto absorb with a simple structure the axial displacement such as thermalexpansion due to the heat generation by the rotor.

In addition, if grease lubrication is adopted, maintenance can beperformed at a small cost by virtue of grease lubrication which is easyto handle and is relatively inexpensive.

In addition, if a grease replenishing unit is provided, it is possibleto replenish the shortage of grease by the grease replenishing unit,making it possible to avoid a seizure and the like.

In addition, if a mechanism is provided for discharging excess greaseafter the supply of grease, the lubricant which is supplied to theinterior of the bearing and has become unnecessary adheres to a rotatingmember such as an outer ring spacer disposed in the vicinity of thebearing. The lubricant adhering to the rotating member is slung off tooutside the bearing by the rotational force. Consequently, the lubricantwhich became unnecessary can be forcibly discharged to outside thebearing.

In addition, if a very small amount of lubrication of any one ofoil-air, oil-mist, and direct-injection lubrication is used, it ispossible to effect highly efficient lubrication through a very smallamount of lubrication of any one of oil-air, oil-mist, anddirect-injection lubrication. Hence anti-seizure properties can beimproved further.

In addition, if an elastic body is arranged between fitting surfaces ofthe sleeve housing and the bearing sleeve made movable in the axialdirection of the rotating shaft by fitting to the sleeve housing, it ispossible to increase the radial stiffness by the elastic body andimprove the damping factor on the axial direction, thereby making itpossible to prevent the self-excited vibration of the rotating shaft. Inaddition, since a fluid for applying pressure is arranged to be suppliedto the elastic body, it is possible to further increase the radialstiffness by allowing the elastic body to be deformed, and enhance theeffect of suppressing the self-excited vibration of the rotating shaftby improving the damping factor on the axial direction.

In addition, the elastic body is an O-ring, and the fluid is compressedair, the compressed air being supplied between the O-rings provided in aplural number, so as to apply the pressure to the O-rings. Therefore, itis possible to effectively prevent the self-excited vibration of therotating shaft by increasing the radial stiffness while maintaining highslidability. In addition, since the O-ring excels in workability andversatility, a high-performance spindle apparatus can be fabricatedwithout requiring a complex manufacturing process.

In addition, if the pressure of the fluid for applying pressure to theelastic body is made variable, the amount of deformation of the elasticbody due to the pressure of the fluid can be varied by changing thepressure in correspondence with the working conditions of the spindleapparatus. In addition, the self-excited vibration of the rotating shaftcan be effectively prevented by setting the radial stiffness and thedamping factor of the elastic body to values optimal to the workingconditions. In addition, the radial stiffness and the damping factor ofthe elastic body can be changed by merely changing the pressure of thefluid supplied, and can be changed very easily.

In addition, the O-ring is formed of nitrile rubber or fluoro rubber,and the interference of the O-ring is set to be not less than 10% of aworking standard value and not more than the working standard value.Therefore, the O-ring has a sealing effect and an elastically supportingeffect, has wear resistance against the axial movement and heatresistance against heat generation, and can thereby be made to have along life. In addition, it is possible to improve the radial stiffnessand the axial damping properties while maintaining the slidability byappropriately increasing the stiffness of the O-ring.

In addition, a plurality of sets of elastic bodies are disposed, each ofthe sets being formed by a plurality of elastic bodies, one of the setsof elastic bodies arranged at both ends being disposed on the bearingsleeve, the other one of the sets of elastic bodies on the sleevehousing. If this arrangement is provided, the assembly is facilitated,and the possibility of causing damage to the O-rings is small. It shouldbe noted that the effect whereby the movement of the bearing sleeve isallowed to take place uniformly an stably in cases where various loadsare applied to the spindle apparatus is identical to a case where theelastic body is disposed only on the bearing sleeve and a case where itis disposed only on the sleeve housing. Further, an arrangement may beprovided such that two elastic bodies are disposed in the spindleapparatus, one on the bearing sleeve and the other on the sleevehousing, and a fluid is supplied to between the elastic bodies.

In addition, the spindle cartridge is inserted in the spindle cartridgegripping portion provided in the axial direction of the spindle head,and the amount of movement in the feeding axis direction parallel to theaxial direction of the rotating shaft is set to be longer than thelength necessary for inserting the spindle cartridge into the spindlehead. The spindle cartridge is thereby capable of being disassembled andassembled integrally with respect to the spindle head. Consequently,since the amount of movement in the Z-axis, which is the feeding axisdirection parallel to the axial direction of the rotating shaft, is setto be longer than the length necessary for inserting the spindlecartridge into the spindle head, it is possible to easily effect thewithdrawal making use of the Z-axis feeding.

In addition, the amount of movement in the feeding axis directionparallel to the axial direction of the rotating shaft is set to belonger than the length necessary for inserting the spindle sub-cartridgeinto the spindle head. The spindle sub-cartridge is thereby capable ofbeing disassembled and assembled integrally with respect to the spindlehead. Consequently, since the amount of movement in the Z-axis, which isthe feeding axis direction parallel to the axial direction of therotating shaft, is set to be longer than the length necessary forinserting the spindle sub-cartridge into the spindle head, it ispossible to easily effect the withdrawal making use of the Z-axisfeeding.

In addition, if the spindle cartridge gripping portion of the spindlehead can be disassembled by being divided at a position for dividing atleast in half, even if, for instance, the amount of Z-axis movement isset to be short, removal and assembly can be performed by dividing anddeveloping the spindle cartridge gripping portion of the spindle head.Further, the stiffness of the entire machine tool can be increased byincreasing the fastening stiffness of the spindle cartridge and thespindle head.

In addition, the rotating shaft with the rotor, the front side bearing,the rear side bearing, the front housing, and the sleeve housing areintegrally assembled to form the spindle sub-cartridge, the spindlesub-cartridge, the outer cylinder, and the tool unclamp cylinder arearranged in a three-divided form, and the spindle sub-cartridge iswithdrawable from the outer cylinder.

Accordingly, since the rotating shaft with the rotor, the front sidebearing, the rear side bearing, the front housing, and the sleevehousing, which make up the spindle sub-cartridge, can be withdrawnintegrally from the outer cylinder, only the rotating shaft, the frontside bearing, and the rear side bearing which require inspection,repair, or replacement can be easily dismounted without disassemblingthe entire spindle apparatus. Consequently, it becomes possible tocontrol any parts making up the spindle cartridge without removing thewirings and pipings.

Here, as the spindle apparatus, it is possible to cite by way of examplean apparatus which rotates at high speed while replaceably gripping amultiplicity of tools. Such a spindle apparatus is subjected to highcutting resistance during the machining of workpieces, so that a toolmounting hole in the spindle becomes worn, a collet and a coned diskspring become damaged, and the bearings become worn or damaged. For thisreason, in cases where repair is conducted for such a failure or troubleat the site of use, it is general practice to perform reassembly afterdisengaging electric wirings for a built-in motor and a limit switch,disassembling the entire spindle apparatus, and replacing the spindle,parts or bearings within the spindle. This repair operation is alarge-scale one, needs high-level expertise and skills, and requires alarge amount of time.

In addition, if the tool unclamp cylinder is withdrawable from the outercylinder, only the tool unclamp cylinder can be easily dismountedwithout disassembling the entire spindle apparatus, so that inspection,repair, or replacement is easily possible for any parts making up thetool unclamp cylinder.

In addition, if an assembly of the tool unclamp cylinder and the outercylinder with the spindle sub-cartridge withdrawn therefrom iswithdrawable from the spindle head, in addition to the spindlesub-cartridge, an assembly of the outer cylinder and the tool unclampcylinder can be easily dismounted from the spindle head withoutdisassembling the entire spindle apparatus. Hence, inspection, repair,or replacement is easily possible for any parts making up the outercylinder or the tool unclamp cylinder.

In addition, if an assembly of the spindle sub-cartridge, the outercylinder, and the tool unclamp cylinder is withdrawable from the spindlehead, an assembly of the spindle sub-cartridge, the outer cylinder, andthe tool unclamp cylinder can be easily dismounted from the spindle headwithout disassembling the entire spindle apparatus. Hence, inspection,repair, or replacement is easily possible for any parts making up thespindle apparatus.

In addition, if a coupler having various fluid pipings and a powersupply coupler is detachably installed on the tool unclamp cylinder orthe outer cylinder, a power supply coupler and opening and closingvalves for the various fluid pipings are provided for the coupler.Consequently, if the operation is performed at the time of inspection,repair, or replacement after closing the various fluid pipings andremoving the power supply wiring, the operation can be performed whilepreventing the leakage of the fluid, entanglement of the power supplywiring, and the like.

In addition, if a sensor for detecting the rotation of the rotatingshaft is disposed between the rotating shaft and the outer cylinder.Consequently, the inspection, repair, or replacement of the sensorbecomes possible by merely removing the tool unclamp cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view illustrating a firstembodiment of the invention;

FIG. 2 is a longitudinal cross-sectional view illustrating asub-assembly in the first embodiment;

FIG. 3 is a front view illustrating a rear cover in the firstembodiment;

FIG. 4 is a longitudinal cross-sectional view illustrating a secondembodiment of the invention;

FIG. 5 is a longitudinal cross-sectional view illustrating thesub-assembly in the second embodiment;

FIG. 6 is a longitudinal cross-sectional view in a tool unclamped statein the second embodiment;

FIG. 7 is a diagram of assembly to an automatic tool changer in thesecond embodiment;

FIG. 8 is a longitudinal cross-sectional view illustrating a thirdembodiment of the invention;

FIG. 9 is a longitudinal cross-sectional view illustrating thesub-assembly in accordance with a third embodiment of the invention;

FIG. 10 is a characteristic diagram of the size and surface pressure ofbearings in the third embodiment;

FIG. 11( a) is a front view of a bearing sleeve in accordance with afourth embodiment of the invention;

FIG. 11( b) is a longitudinal cross-sectional view of FIG. 11( a);

FIG. 12 is a longitudinal cross-sectional view of essential portionsillustrating a modification of the fourth embodiment;

FIG. 13 is a longitudinal cross-sectional view of a fifth embodiment ofthe invention;

FIG. 14 is an enlarged longitudinal cross-sectional view of a sleeveportion in the fifth embodiment;

FIG. 15 is an enlarged longitudinal cross-sectional view of essentialportions illustrating a state in which an elastic body is deformed bythe pressure of a fluid supplied in the fifth embodiment;

FIG. 16 is an enlarged longitudinal cross-sectional view of essentialportions of a testing device for measuring various characteristics ofthe sleeve portion in the fifth embodiment;

FIG. 17 is a side elevational view illustrating a sixth embodiment ofthe invention;

FIG. 18 is a cross-sectional view of a spindle cartridge used in thesixth embodiment;

FIG. 19 is a side elevational view illustrating a seventh embodiment ofthe invention;

FIG. 20 is a cross-sectional view of a spindle sub-cartridge used in theseventh embodiment;

FIG. 21 is an explanatory diagram illustrating the procedure fordismounting the spindle sub-cartridge in the seventh embodiment;

FIG. 22 is an explanatory diagram illustrating the procedure fordismounting the spindle sub-cartridge in the seventh embodiment;

FIG. 23 is an explanatory diagram illustrating the procedure fordismounting the spindle sub-cartridge in the seventh embodiment;

FIG. 24 is a side elevational view illustrating an eighth embodiment ofthe invention;

FIG. 25 is a cross-sectional view illustrating a ninth embodiment of theinvention;

FIG. 26 is a cross-sectional view of a state in which the spindlesub-cartridge is withdrawn from an outer cylinder in accordance with theninth embodiment;

FIG. 27 is a cross-sectional view of a state in which a tool unclampcylinder is withdrawn from the outer cylinder in accordance with theninth embodiment;

FIG. 28 is a cross-sectional view of a state in which an assembly of thetool unclamp cylinder and the outer cylinder with the spindlesub-cartridge withdrawn therefrom is withdrawn from a spindle head inaccordance with the ninth embodiment;

FIG. 29 is a cross-sectional view of a state in which an assembly of thespindle sub-cartridge, the outer cylinder, and the tool unclamp cylinderis withdrawn from the spindle head in accordance with the ninthembodiment;

FIG. 30 is a cross-sectional view illustrating a 10th embodiment of theinvention; and

FIG. 31 is a longitudinal cross-sectional view of a conventional spindleapparatus.

It should be noted that, in the drawings, reference numeral 1 denotes aspindle apparatus; 2, sub-assembly; 3, outer cylinder; 4, stator; 5,sleeve housing; 6, rotating shaft; 7, rotor; 8, front housing; 9, rearcover; 11, bearing sleeve; 12, front side bearing; 13, rear sidebearing; 14, piston mechanism; 30, spindle apparatus; 31, insidediameter part; 32, spring; 33, inside diameter part-side adjustment part(adjustment part); 34, piston; 39, mounting reference plane; 40, spindleapparatus; 50, spindle apparatus; 60, spindle apparatus; 61, sleevehousing; 62, lubricant supplying port (lubricant supplying passage); 63,bearing sleeve; 64, circumferential groove; 65, radial hole (lubricantsupplying passage); 66, front-side O-ring (O-ring); 67, rear-side O-ring(O-ring); 71, lubricant discharging hole; 72, O-ring; 80, spindleapparatus; 81, rotating shaft; 82, front side bearing; 83, front sidebearing; 84, bearing sleeve; 85, rear side bearing; 86, rear sidebearing; 87, front housing; 88, sleeve housing; 89, outer ring; 90,outer ring; 91, inner ring; 92, inner ring; 94, O-ring (elastic body);97, inner ring; 98, inner ring; 99, outer ring; 100, outer ring; 120,machine tool; 121, rotating shaft; 122, front side bearing; 123, innerring; 124, outer ring; 125, front housing; 126, built-in motor; 127,rotor; 128, stator; 129, inner ring; 130, rear side bearing; 131,spindle head; 132, outer cylinder; 133, spindle cartridge (spindleapparatus); 134, spindle cartridge gripping portion; 142, bearingsleeve; 145, rear housing; 150, machine tool; 151, spindlesub-cartridge; 160, machine tool; 161, spindle head; 180, spindleapparatus; 181, outer cylinder; 182, stator; 183, spindle head; 184,rotating shaft; 185, rotor, 186, front side bearing; 187, inner ring;188, rear side bearing; 189, inner ring; 190, outer ring; 191; fronthousing; 192, outer ring; 193, sleeve housing; 194, tool unclampcylinder; 195, spindle sub-cartridge; 196, first assembly (assembly);197, second assembly (assembly); 198, rotation sensor (sensor); 207,cooling oil supplying hose (various fluid piping); 220, spindleapparatus; 221, coupler; 222, spindle cartridge; 224, oil pressuresupplying hose (various fluid piping); 226, sleeve housing; and 230,power supply coupler.

BEST MODES FOR CARRYING OUT THE INVENTION

FIGS. 1 to 3 show a first embodiment of the invention. It should benoted that the characteristics of this embodiment are as follows: Thediameter becomes smaller in the order of the inner peripheral diameterφA of an outer cylinder 3, the inside diameter φB′ of a stator 4, andthe outside diameter φC of a bearing sleeve 11. A sub-assembly 2 made upof a front housing 8, a rotating shaft 6, and the bearing sleeve 11 iswithdrawable from the outer cylinder 3. The radius of a rotating part inan arbitrary section located rearwardly of the bearing sleeve 11 issmaller than a minimum radius of a non-rotating part between a rear endof the bearing sleeve 11 and that section, or the diameter of therotating part in an arbitrary section located rearwardly of the bearingsleeve 11 is smaller than a minimum diameter of the non-rotating partbetween the rear end of the bearing sleeve 11 and that section.

As shown in FIG. 1, a spindle apparatus 1 in accordance with the firstembodiment includes the outer cylinder 3 having the stator 4 and asleeve housing 5; the rotatable rotating shaft 6 having a rotor 7; and afront side bearing 12 which is an arrangement angular contact ballbearing having outer rings fixed to the front housing 8 and inner ringsfitted over one end of the rotating shaft 6. The spindle apparatus 1further includes the bearing sleeve 11 disposed on the other end side ofthe rotating shaft 6 and fitted in the sleeve housing 5 so as to bemovable in the axial direction of the rotating shaft 6; and a rear sidebearing 13 which is a paired arrangement angular contact ball bearinghaving inner rings fitted over the other end of the rotating shaft 6 andouter rings fixed to the bearing sleeve 11 to rotatably support therotating shaft 6 in cooperation with the frontside bearing 12. Referencenumeral 14 denotes a piston mechanism for tool replacement. It should benoted that the sleeve housing 5 and the outer cylinder 3 may be formedas an integral structure.

As shown in FIG. 2, the sub-assembly 2 made up of the front housing 8,the rotating shaft 6, and the bearing sleeve 11 is constructed so as tobe withdrawable from the outer cylinder 3. Namely, in the spindleapparatus 1 of this embodiment, the diameter becomes smaller in theorder of the inner peripheral diameter φA of the outer cylinder 3, theoutside diameter φB of the rotor 7, and the outside diameter φC of thebearing sleeve 11 (φA>φB>φC). Alternatively, with respect to the statorinside diameter φB′ (see FIG. 1) instead of the rotor inside diameterφB, an arrangement may be provided such that φA>φB′>φC. In addition, ina range L located rearwardly of the bearing sleeve 11, the outsidediameter of the sub-assembly 2 is set to be smaller than the outsidediameter of the bearing sleeve 11. Namely, to ensure that thenon-rotating part does not constitute a hindrance when an attempt ismade to withdraw the spindle in the direction of arrow M, the outsidediameter of the rotating part of the spindle in an arbitrary section inthe range L is made smaller than a minimum inner peripheral diameter ofthe non-rotating part between that section and the rear end of thebearing sleeve. Thus, the outside diameter of the rotating part isdefined so that the non-rotating part does not constitute a hindrance.Accordingly, when an attempt is made to withdraw the sub-assembly 2 inthe direction M in the drawing, the piston mechanism 14 and the like,which are a non-rotating part, for holding/releasing a tool W which isinstalled in a left end portion in the drawing do not constitute ahindrance (see FIG. 1).

In addition, in the spindle apparatus 1, a clearance fit of 5 to 30 μmis provided for the outside diameter of the bearing sleeve 11 withrespect to the inside diameter of the sleeve housing 5. Further, in thespindle apparatus 1, the rear side bearing 13 is a back-to-backarrangement angular contact ball bearing with fixed-position preload. Asa result, the rear side bearing 13 and the bearing sleeve 11 functionmainly to support the rotating shaft 6, but are capable of absorbingwith a simple structure the axial displacement such as thermal expansiondue to the heat generation by the rotor.

In addition, in the spindle apparatus 1, an interference fit of 0 to 20μm is provided for an inlay portion 15 between the front housing 8 andan inner peripheral surface of the outer cylinder 3. As a result, theaxes of the front housing 8 and the outer cylinder 3 do not becomemisaligned. In addition, as for matching surfaces 16, the front housing8 and the outer cylinder 3 are finished to high precision with aperpendicularity of 2 to 5 μm or less with respect to the axis. As aresult, even if the length LR of the inlay portion 15 is short, the axesof the two members are aligned. If the length of the inlay portion 15 islong, the assembling efficiency is poor; however, in this embodiment,the inlay length LR is made short at about 1/10 to 1/30 of the inlaydiameter φA. In addition, since the length LR of the inlay portion 15 isshort, the front housing 8 and the outer cylinder 3 can be easilyassembled by being tightened by assembling bolts 17. As a result, thereis no need of the alignment operation.

In addition, in the sub-assembly 2, labyrinth seals L1 to L4 are formedwith respect to the outside air. During the use of the spindle, theentry of foreign objects of such as a cutting fluid and cuttings isprevented by the powerful labyrinths L1 and L4. In cases such as whenonly the sub-assembly 2 is kept in stock, foreign objects such as dustare shut off by the labyrinths L1 to L4. The labyrinths L2 and L3function to prevent the entry of foreign objects during the replacementof the sub-assembly due to maintenance. At the time of the maintenance,since it is impossible to expect an environment where the amount offoreign objects is small, such as a cleanroom, the labyrinths L2 and L3are useful. The structures of the labyrinths L3 and L4 are realizable bythe use of the bearing sleeve 11.

As shown in FIG. 3, as for the rear portion of a rear cover 9, sevenwirings (motor power lines 25, a motor temperature sensor line 26, arotary encoder line, etc. (partly not shown)), 14 pipings (bearinglubricating pipings 21, coolant oil pipings 22, tool unclampinghydraulic pipings 23, a tool tapered air-blow piping 24, and an air sealpiping 28) are connected to the outside. Therefore, at the time ofmaintenance, none of these need to be handled, so that downtime is veryshort, and the maintenance efficiency is excellent.

According to the above-described spindle apparatus 10, the sub-assembly2 made up of the front housing 8, the rotating shaft 6, and the bearingsleeve 11 is withdrawable from the outer cylinder 3. For this reason,the assembling efficiency improves and the sub-assembly 2 can bereplaced speedily when it is broken. In addition, as for the bearingsleeve 11, since the rear side bearing 13 is in an assembled state, thestate of grease does not change by the withdrawal of the sub-assembly 2.Accordingly, as the sub-assembly 2 is kept in stock after performing therunning-in operation in advance by using another outer cylinder, thesub-assembly can be replaced at the time of the damage of the spindleapparatus, and the normal operation is made possible immediately,thereby permitting a substantial reduction in downtime. In addition, acost reduction is made possible in comparison with the replacement ofthe entire spindle apparatus 1, and a reduction in inventory cost isalso made possible.

FIGS. 4 to 7 show a second embodiment of the invention. Thecharacteristics of this embodiment lie in that an inside diameter part31 is incorporated so as to be capable of compressing springs 32, thatan adjustment part 33 is fixed to a rear portion of the inside diameterpart 31, and that a piston pressing surface 34 for the piston mechanism14 is formed on the adjustment part 33. Since the other arrangements areidentical to those of the first embodiment, identical members will bedenoted by the same reference numerals, and a detailed descriptionthereof will be omitted.

As shown in FIG. 4, in a spindle apparatus 30 in accordance with thesecond embodiment, the inside diameter part (also referred to as adrawbar) 31, which is capable of compressing the two springs 32 and ofreplacing the tool, is incorporated in the rotating shaft 6 whichrotates together with the rotor 7 as the stator 4 of the outer cylinder3 is energized. Further, the inside diameter part-side adjustment part33 is installed on a rear end portion of the inside diameter part 31.The piston pressing surface 34 for the piston mechanism 14 is formed atan end portion of the inside diameter part-side adjustment part 33. Apiston-side adjustment part 36 for pressing the inside diameterpart-side adjustment part 33 is installed on an end portion of a piston35 of the piston mechanism 14.

As for the piston mechanism 14, as a pressure medium such as oil, water,air, or the like is introduced into an advance-side pressure introducingportion 37, the piston 35 is advanced. Hence, the piston-side adjustmentpart 36 of the piston 35 presses the piston pressing surface 34 of theinside diameter part-side adjustment part 33, thereby pressing andmoving the inside diameter part 31 in the axial direction to push outthe tool W and assume a tool unclamped state. In contrast, as thepressure within the advance-side pressure introducing portion 37 isreleased, and the pressure medium is introduced into a return-sidepressure introducing portion 38, the piston 35 is returned, therebypressing and moving the inside diameter part 31 in the axial directionto assume a tool clamped state.

As shown in FIG. 5, the inside diameter part-side adjustment part 33 iscapable of adjusting an axial dimension (distance) Z between a mountingreference plane 39 of the sub-assembly 2 and the piston pressing surface34 in the inside diameter part 31 to within ±0.1 mm relative to thereference dimension. Namely, as for the sub-assembly 2, a dimensionaldifference occurs in the axial dimension Z from the mounting referenceplane 39 to the piston pressing surface 34 in the inside diameter part31 due to the stacking of the multiplicity of parts. For this reason,unless adjustment is effected in advance, it is necessary to perform theadjustment operation of the piston stroke at the site. For example, ifthe amount of movement (amount of pushing out) of the inside diameterpart 31 becomes small due to a shortage of the piston stroke, a toolholder cannot unclamp. If the amount of movement of the inside diameterpart 31 is too large to the contrary, the inside diameter part 31excessively presses the holder forward, so that an automatic toolchanger (ATC) 40 (see FIG. 7) becomes unable to grip the tool holder. Incontrast, if it is assumed that the tool holder pushing amount (theamount of the tool holder pushed out from the grip position by theinside diameter part 31 when the piston 35 is pushed to a foremost end)is 0.4 mm to 0.6 mm, the inside diameter part-side adjustment part 33adjusts its tolerance to within ±0.1 mm, which is 0.1 mm to 0.2 mm orthereabouts, thereby making it possible to appropriately effectunclamping. As a result, piston adjustment is made unnecessary at thetime of performing replacement of the sub-assembly, making it possibleto improve the maintenance efficiency.

Here, as for the adjustment based on the inside diameter part-sideadjustment part 33, it is possible to cite, among others, a method inwhich cutting (turning and grinding) work is performed by providing astock allowance in advance, a method in which a shim having a varyingthickness is inserted in the gap S, a method in which an adjustmentplate is selected from adjustment plates of various sizes prepared inadvance and is installed, and a method in which an adjustment plate isdisposed at a desired position by an adjustment screw and is fixed by ananaerobic adhesive or the like. Furthermore, a large-size jig isrequired to directly measure the axial dimension Z, and there are caseswhere the sub-assembly, which is a heavy piece, must be set on the jig.Therefore, to simplify the adjustment operation, there are cases wheredimensional control of some degree is provided for various parts. Forexample, it is possible to cite a method in which a dimension A, adimension B (both of the inner ring spacer and the outer ring spacer), adifferential width C between rearmost-side inner and outer rings of thefront side bearing 12, and a dimension D are controlled in advance, andonly a dimension ZZ is measured and adjusted with the inside diameterpart 31 fitted to the rotating shaft 6. With this method, since it isunnecessary to control axial dimensions of spindle inside diameterportions (e.g., various dimensions of a collet portion, displacement ofthe tool's taper, and the hole depth of the inside diameter part 31), itis possible to reduce the cost of dimensional control, and the burden ofthe adjustment operation is small. It should be noted that a universalarrangement bearing for which all the differential widths between thefront face and the back face are adjusted individually may be used forthe four rows of the front side bearing 12 to simplify the control ofthe differential width C.

As shown in FIGS. 4 to 6, a tool holder pushing amount (see FIG. 6) E isadjusted by using the sub-assembly 2 for which the axial dimension Z iscontrolled.

Since tool holder pushing amount E=(piston stroke F)−(space G)−(spaceH), either the respective amounts of the right-hand side are measured,or the pushing amount E (the amount by which the tool holder advances)is measured by actually effecting the unclamping. Then, here, thepiston-side adjustment part 36 is machined for adjustment such thatE=0.5±0.1 mm. Consequently, the axial position of the clamp-unclampstroke is determined. As a result, in the case of the replacement of themutually adjusted subassemblies 2 the adjustment of the piston portionis subsequently made unnecessary since the positional relationshipbetween the piston 35 and the inside diameter part 31 does not change.

By so doing, with respect to the tolerance of the axial dimension Z fromthe mounting reference plane 39 to the piston pressing surface 34, thesub-assembly 2 is controlled to a value smaller than the tolerance of0.1 mm to 0.2 mm of the tool holder pressing amount E. When the pistonmechanism 14 for tool replacement is assembled, the piston stroke F isadjusted in accordance with this controlled sub-assembly 2.Consequently, if the units of the subassemblies 2 whose axial dimensionsZ are controlled are replaced with each other at the time ofmaintenance, the axial phase relationship of the piston pressing surface34 of the inside diameter part 31 does not change, so that thereadjustment of the piston stroke becomes unnecessary. In addition,since the axial dimension Z is determined by the stacking of themultiplicity of parts, tolerances of axial dimensions of these parts maybe respectively set, and control may be provided such that a value oftheir accumulation assumes a desired value or less. However, such amethod, i.e., to satisfy the tolerance of 0.1 to 0.2 mm by theaccumulation of, specifically, 10 or more dimensional tolerances, oftenleads to higher cost and an increase in the fraction defective.Accordingly, the axial dimension Z can be controlled at very low cost byassembling the inside diameter part-side adjustment part 33 to the rearportion of the inside diameter part 31 after making adjustmentsubsequent to the assembly of the inside diameter part 31.

As shown in FIG. 6, as for the piston mechanism 14, as the pressuremedium is introduced into the advance-side pressure introducing portion37, the piston 35 is reciprocated, causing the piston-side adjustmentpart 36 to press the piston pressing surface 34 of the inside diameterpart-side adjustment part 33. Hence, the inside diameter part 31 ispressed and moved in the axial direction against the springs 32 to pushout the tool W, thereby assuming the tool unclamped state.

As shown in FIG. 7, at the time of the automatic tool replacement of thespindle apparatus 30, the operation of the automatic tool changer 40 isvery fast for improvement of the efficiency, and the replacement time isnormally 0.2 to 1.5 seconds or thereabouts. For this reason, it isnecessary to maintain the strength and stiffness of the respective partsto a high level. The automatic tool changer 40 operates such that afteran arm 41 has gripped the rotating shaft 6 and a tool holder 43 of atool magazine 42, the tool W in the rotating shaft 6 is unclamped, andthe arm 41 undergoes vertical and swiveling operation to allow toolreplacement. When the tool W is gripped and the rotating shaft 6 isunclamped, if the amount of pushing of the tool holder 43 is too large,since the tool holder 43 has high stiffness and is being gripped by thearm 41, an excessive load is applied to the arm 41. Hence, a failure ofthe automatic tool changer 40 can result. For this reason, the amount ofpushing of the tool holder 43 needs to be set to 0.5 to 0.6 mm or less.With the spindle apparatus 30, even if maintenance is performed and thesub-assembly 2 is replaced, the amount of pushing of the tool holder 43does not change, so that adjustment does not involve much time andtrouble, and replacement in a short period of time becomes possible.

FIGS. 8 to 10 show a third embodiment of the invention. Thecharacteristic of this embodiment lies in that a ratio between, on theone hand, a fitting length J of the bearing sleeve 11 and the sleevehousing 5 and, on the other hand, an outside diameter I of the bearingsleeve 11 is set within the range of “fitting length J/outside diameterI=0.45 to 0.8.” Since the other arrangements are identical to those ofthe first embodiment, identical members will be denoted by the samereference numerals, and a detailed description thereof will be omitted.

Referring to FIG. 8, a description will be given of the third embodimentof the spindle apparatus in accordance with the invention. It should benoted that, in FIG. 8, an upper half in the drawing illustrates the toolunclamped state, and a lower half in the drawing illustrates the toolclamped state.

As shown in FIG. 8, in a spindle apparatus 50 in accordance with thethird embodiment, an inside diameter part 51 having a different coneangle is used for the sub-assembly 2. At this time, inside diameterparts for BT holders (JIS B 6339) and HSK holders (ISO-12164) areadjusted so as to be interchangeable with those shown in FIGS. 1 and 4,although there are variations in a target value Z1 to be controlled withrespect to the axial dimension Z owing to the standards of the tooltaper. Namely, adjustment is made such that an axial dimension Z_(UC2)at the time of unclamping becomes identical to an unclamped stateZ_(UC1) shown in FIG. 6. It should be noted that the space G in FIG. 4is set to a value greater than a minimum necessary amount for unclampingthe BT holder for the purpose of application to inside diameter partshaving thus different axial dimensions Z. There are cases where varioustool taper standards are used depending on applications, but sinceinterchangeability is provided to permit unclamping in different toolstandards as in this embodiment, a change in specifications isfacilitate, and the inventory control of inner cartridges formaintenance is facilitated, thereby attaining a reduction in the cost.

In addition, as shown in FIG. 9, in the spindle apparatus 50, the ratiobetween the outside diameter I of the bearing sleeve 11 and the length Jof its fitting portion is set such that J/I≈0.5. In this case, therelationship between the outside diameter I and the length J shouldpreferably be set to be 0.45 to 0.8. When the sub-assembly 2 is insertedinto the outer cylinder 3, the bearing sleeve 11 is first fitted to theinside diameter of the sleeve housing 5. Since the replacement of thesub-assembly 2 is generally performed at the work site of the machinetool user, there are many cases where a special jig cannot be used inthe replacement operation. In such a case, if the sub-assembly 2 issubjected to a force acting in a direction K, such as its own weight, amoment load is applied to the rear side bearing 13. At that juncture, ifthe length J is small, the span M of the two rows of the rear sidebearing 13 becomes short, and contact pressure becomes large, possiblydamaging the rear side bearing 13.

As shown in FIG. 10, in the spindle apparatus 50, examinations are madeof the relationship between the above-described J/I and the bearing spanand the relationship of the contact pressure generated in the rear sidebearing 13 at the time when a load K is applied. The load K is theself-weight of the sub-assembly 2 and is a load which is generated byhandling at the time of assembly in the replacement operation at a sitewhere a jig cannot be united. The rear side bearing 13 is an angularcontact ball bearing with an inside diameter of φ55 mm. As for thecontact pressure of the bearing, it is known that, in a bearing steelwith a hardness Hv=700, an indentation occurs at 3.5 GPa or more. Fromthese, it can be understood that “J/I≧0.45” is necessary. Meanwhile, ifthe span of the rear side bearing 13 is made too long, the performanceof the machine tool cannot be improved, and problems occur such as anincrease in the inertial moment of the spindle (an increase in theacceleration/deceleration time) and a decline in a resonance point.Therefore, it is desirable to provide a setting such that J/I≦0.8.Furthermore, by setting the relationship of J/I as described above, anO-ring which exhibits vibration damping action, which will be describedlater, can be provided. As the relationship between the outside diameterI of the bearing sleeve 11 and the length J of its fitting portion isthus set and designed appropriately, it is possible to obtain thestructure of the sub-assembly 2 excelling in the maintenance efficiencyand the performance of the machine tool.

FIGS. 11( a), 11(b), and 12 show a fourth embodiment of the invention.The characteristic of this embodiment lies in that there are provided aplurality of lubricant discharging holes 71 provided circumferentiallyin the bearing sleeve 11, circumferential grooves 64 provided in afitting surface of the outer periphery of the bearing sleeve 11, andradial lubricant supplying passages 62 and 65 communicatingly connectedto the circumferential grooves 64. Since the other arrangements areidentical to those of the first embodiment, identical members will bedenoted by the same reference numerals, and a detailed descriptionthereof will be omitted.

As shown in FIGS. 11( a) and 11(b), in a spindle apparatus 60 inaccordance with the fourth embodiment, lubricant supplying anddischarging structures are disposed in the rear side bearing 13, and astructure which makes it unnecessary to determine the phase is providedto permit easy removal and assembly of the sub-assembly 2.

In addition, the bearing sleeve 11 is clearance-fitted with respect tothe inside diameter of the sleeve housing 5 (see FIG. 6). As a result,the bearing sleeve 11 easily rotates relative to the rotating shaft 6 ina state in which the inside diameter part 31 is assembled thereto.Accordingly, in a case where a lubricant is supplied to the rear sidebearing 13, projections, such as a nozzle and a key, for determining itssupply phase and a lubricant discharge hole phase are conventionallyprovided. For this reason, there has been a problem in that unless phaseadjustment and withdrawal and insertion of the projecting parts areeffected, the assembly and separation of the sub-assembly 2 cannot beperformed, making maintenance difficult. In contrast, since projectionssuch as the lubricating nozzle are not provided on the outer peripheryof the sub-assembly 2, the removal of the sub-assembly 2 becomespossible only by removing the assembling bolts 17.

As for the lubricant supplying structure, a lubricant is supplied intothe bearing space through the outer rings of the rear side bearing 13 bymeans of the radial lubricant supplying passages 62 communicatinglyconnected to a lubricant replenishing device (not shown), thecircumferential grooves 64 provided in a fitting surface of the outerperiphery of a bearing sleeve 63, and the radial holes (lubricantsupplying passages) 65 formed in communication with the circumferentialgrooves 64. Further, as for the sleeve housing 61 and the bearing sleeve63, their front-side end portions are sealed by front-side O-rings 66and 66, while their rear-side end portions are sealed by rear-sideO-rings 67 and 67. At this time, even if the radial lubricant supplyingpassages of the sleeve housing 61 and the bearing sleeve 63 are in thesame phase, or the two members rotate in a counter phase of 180°, thelubricating oil is supplied smoothly to the rear side bearing 13. Itshould be noted that the circumferential grooves 64 are provided in theinner periphery of the sleeve housing 61.

The discharging structure consists of radial discharging holes 69, 69,and 69 formed radially by outer ring spacers 68 and 68 respectivelydisposed between the rows of the rear side bearing 13, an outer ringpresser 68A, and the bearing sleeve 63; an axial discharging hole 70formed axially in the bearing sleeve 63 in communication with the radialdischarging holes 69, 69, and 69; and the plurality of, i.e., six,lubricant discharging holes 71, 71, 71, 71, 71, and 71 providedcircumferentially in the bearing sleeve 63 at equal intervals incommunication with the axial discharging hole 70. Since the sixlubricant discharging holes 71, 71, 71, 71, 71, and 71 are disposed inequally distributed form, at least one lubricant discharging hole 71 issecured within a range of a position located directly below ±15° atwhatever phase. Thus, discharging at the time of horizontal mounting ismade possible.

The lubricant supplying and discharging structures have the function ofdischarging excess grease after grease is supplied. As a result, thelubricant which is supplied to the interior of the bearing and becomesunnecessary is slung off to outside the bearing by the rotational forceof a slinger portion 68B in FIG. 12 disposed in the vicinity of thebearing. Consequently, it becomes possible to discharge the lubricantwithout a problem at whatever phase. Although a discharging hole isrequired on the lower side in the case of, for instance, a horizontallymounted spindle, discharging can be effected since one of the holesfaces the lower side. Furthermore, since grease lubrication is adopted,maintenance can be performed at a small cost by virtue of greaselubrication which is easy to handle and is relatively inexpensive. Inaddition, since a lubricant feeding device (grease replenishing unit) isprovided, it is possible to replenish the shortage of grease, making itpossible to avoid a seizure and the like. Furthermore, it is possible touse a very small amount of lubrication of any one of oil-air, oil-mist,and direct-injection lubrication. By so doing, it is possible to effecthighly efficient lubrication, so that anti-seizure properties can beimproved further.

Then, in the sleeve housing 61 and the bearing sleeve 63, to prevent thebreakage of O-rings at the time of withdrawal and insertion of thebearing sleeve, the front-side O-rings 66 and 66 are disposed on thefront-side outer periphery of the bearing sleeve 63, while the rear-sideO-rings 67 and 67 are disposed on the rear-side inner periphery of thesleeve housing 61. As a result, when the bearing sleeve 63 slides on theinner periphery of the sleeve housing 61 in the insertion or withdrawalof the sub-assembly 2, the distance slid by the O-rings 66, 66, 67, and67 is made shortest. At the same time, since the O-rings 66, 66, 67, and67 do not pass steps or holes constituting factors of O-ring breakage,the reliability of the O-rings 66, 66, 67, and 67 can be improvedremarkably.

In addition, as for the O-rings 66, 66, 67, and 67, multiplicities ofO-rings are used, two on the front end side and two on the rear endside. This is for the purpose of damping the vibration of the bearingsleeve 63 through the damping effect based on the interference of therespective O-rings 66, 66, 67, and 67. Since the bearing sleeve 63 isclearance-fitted to the sleeve housing 61, the bearing sleeve 63vibrates in the gap unless damping elements such as O-rings areprovided. If the vibration is large, the cutting performance andaccuracy of the machine tool deteriorates, and the inside diameter ofthe sleeve housing 61 or the outside diameter of the bearing sleeve 63is possibly subjected to fretting wear. If the fretting wear occurs, thevibration increases further, or faulty sliding results. Further, theentire spindle apparatus must be replaced in its repair. In addition,since the force of constraint increases by using the plurality ofO-rings, the bearing sleeve 63 ceases to rotate freely in the rotatingdirection, so that it becomes possible to prevent creep and also preventthe creep wear of fitting surfaces. Thus, by using the plurality ofO-rings, it becomes possible to exhibit even greater effects.

As shown in FIG. 12, in a modification of the fourth embodiment, asingle small-diameter O-ring 72 is used only on the rear side of thebearing sleeve 63. By so doing, the number of the O-rings can bereduced, so that O-rings can be disposed compactly. However, thearrangement shown in FIGS. 11 a and 11 b excels in that the bearingsleeve 63 is not subjected to axial force owing to the pressure of thelubricant.

It should be noted that the spindle apparatuses in accordance with thefirst, second, third, and fourth embodiments are not limited to theabove-described modes for carrying out the invention, and appropriatemodifications, improvements, and the like are possible.

For example, in addition to being applied to a machining center, thespindle apparatus may be applied to an NC machine tool, a generalpurpose machine tool for effecting feeding operation manually, and thelike.

In addition, the front and rear side bearings are not limited to angularcontact ball bearings, and may be deep groove ball bearings or rollingbearings such as various roller bearings.

FIGS. 13 to 16 show a fifth embodiment of the invention. Thecharacteristics of this embodiment lie in that an elastic body 94 forsealing a sleeve housing 88 and a bearing sleeve 84 is provided betweenfitting surfaces of the sleeve housing 88 and the bearing sleeve 84, andthat a fluid for applying pressure is arranged to be supplied to theelastic body 94.

As shown in FIGS. 13 and 14, a spindle apparatus 80 in accordance withthe fifth embodiment includes a rotating shaft 81; a pair of rollingbearings 82 and 83 which are front side bearings; the bearing sleeve 84;a pair of rolling bearings 85 and 86 which are rear side bearings; afront housing 87; and the sleeve housing 88. The sleeve housing 88 isfixed to the front housing 87 and virtually functions as a part of thefront housing 87.

The pair of rolling bearings 82 and 83 are front side bearings havingouter rings 89 and 90 fixed to the front housing 87 and inner rings 91and 92 fitted and fixed to one end of the rotating shaft 81, such thattheir relative position with respect to the front housing 87 is fixed,so as to rotatably support the rotating shaft 81.

The bearing sleeve 84 is fitted in an inside diameter surface 93 of thesleeve housing 88 disposed on the other end side of the rotating shaft81, and is disposed movable in the axial direction. The gap C betweenthe bearing sleeve 84 and the inside-diameter surface 93 of the sleevehousing 88 is determined by taking into account the sleeve dimensions,required stiffness, thermal expansion due to the heat generationaccompanying the rotation of the rotating shaft 81, and the like, and isdesigned by being appropriately selected from the range of 1 to 200 μm.If the gap C is too small, there is a possibility of the bearing sleeve84 and the inside diameter surface 93 of the sleeve housing 88 cominginto contact with each other. On the other hand, if the gap C is toolarge, the center position of the bearing sleeve 84 tends to becomeunstable.

Between the fitting surfaces of the bearing sleeve 84 and the insidediameter surface 93, O-rings 94, which are examples of the elasticbodies, are disposed two each at each end portion, i.e., a total of fourO-rings 94 are disposed. A plurality of O-rings are combined toconstitute one set. In this embodiment, two sets of O-rings arerespectively disposed at both ends of an outer peripheral surface 95 ofthe bearing sleeve 84.

Namely, the two O-rings 94 disposed on a side close to the front sidebearings 82 and 83 are installed in O-ring grooves 96 provided in theinside diameter surface 93 of the sleeve housing 88. Meanwhile, the twoO-rings 94 disposed on a side far from the front side bearings 82 and 83are installed in O-ring grooves 97 provided in the outside diametersurface 95 of the bearing sleeve 84. It should be noted that anarrangement may be provided such that, to the contrary of thearrangement of this embodiment, the O-ring grooves are provided in anouter peripheral surface of the sleeve on the side close to the frontside bearings 82 and 83, while the O-ring bearings are provided in thesleeve housing on the side far from the front side bearings. Stillalternatively, an arrangement may be provided such that the O-ringgrooves are provided only in the outer peripheral surface of the sleeve,or the O-ring grooves are provided only in the sleeve housing.

The interference of the O-ring 94 is desirably set to not more than aworking standard value of the O-ring 94 and not less than 10% of theworking standard value. For instance, the interference in the case of anO-ring 94 with an inside diameter of 84.5 mm and a size of 2 mm isdesirably set to not less than 0.05 mm and not more than 0.5 mm(standard values used are generally provided by O-ring manufacturers asrecommended values, and the working standard value in the case of theaforementioned O-ring 94 is 0.3 to 0.6 mm). It should be noted that theworking standard value is set to 15 to 20% of the average diameter ofthe elastic body such as the O-ring. Preferably, the standard referencevalue used is set to 0.2 mm to 0.4 mm. In addition, it is possible touse the elastic body is not limited to the O-ring 94, and rubber packingor metallic packing having sealing properties.

Here, the reason the upper limit of the interference in the O-ring 94 isset to not more than the working standard value is that if it is set tobe greater than the same, the slidability of the bearing sleeve 84becomes poor, and the amount of displacement of the O-ring 94 becomeslarge, possibly resulting in a short life of the O-ring 94. In addition,the reason the lower limit of the interference is set to be not lessthan 10% of the standard value is that if it becomes smaller than thesame, the sealing properties of the O-ring 94 become poor.

The pair of rolling bearings 85 and 86 are rear side bearings havinginner rings 97 and 98 fitted over the other end of the rotating shaft 81and outer rings 99 and 100 fitted in the bearing sleeve 84 and fixed tothe bearing sleeve 84 by an outer ring presser 101, and are movable inthe axial direction of the rotating shaft 81 together with the bearingsleeve 84. Further, the pair of rolling bearings 85 and 86 rotatablysupport the rotating shaft 81 in cooperation with the front sidebearings 82 and 83. A preload spring 102 is installed between the sleevehousing 88 and the outer ring presser 101, and applies preload to therolling bearings 85 and 86 and the rolling bearings 82 and 83 by pullingthe bearing sleeve 84 rearwardly by means of the outer ring presser 101.It should be noted that in the case of fixed-pressure preload, there arecases where a preload spring is not provided under fixed-positionpreload.

A fluid supplying passage 104 in which a fluid supplying port is openbetween the pair of O-rings 94 is provided in the sleeve housing 88. Thefluid supplying passage is connected to a compressed fluid supplyingdevice (not shown) disposed on an outer side of the spindle apparatus80, and a compressed fluid is supplied thereto from the compressed fluidsupplying device so as to supply the compressed fluid between the pairof O-rings 94. The compressed fluid supplying device is, for example, acompressor, and the fluid is, for example, air.

Next, a description will be given of the operation of this embodiment.As shown in FIGS. 13 and 14, in the spindle apparatus 80, when therotating shaft 81 rotates, the temperature rises due to such asfrictional heat generated. As a result, the rotating shaft 81 becomeselongated in the axial direction, but the pair of rolling bearings 85 an86 which are the rear side bearings move in the axial direction(rightwardly in FIG. 1) together with the bearing sleeve 84, and absorbsthe elongation of the rotating shaft 81 due to the heat. At the sametime, the bearing sleeve undergoes thermal expansion, and its outsidediameter becomes large, so that the gap C with the sleeve housing 88becomes small. Therefore, the gap C is set to, for example, 10 μm orthereabouts by estimating the thermal expansion in advance. If the gap Cis large, radial stiffness declines. Actually, however, since theplurality of O-rings 94 are disposed between the bearing sleeve 84 andthe sleeve housing 88 in a state of being crushed by the portion of theinterference, the radial stiffness is increased by the O-rings 94,suppressing the vibration of the rotating shaft 81.

As shown in FIG. 15, when compressed air is supplied under pressure inthe direction of arrow A from the compressor, i.e., the compressed fluidsupplying device, through the fluid supplying passage 104, and issupplied between the pair of O-rings 94, the pair of O-rings 94 whichare installed by being fitted in the O-ring grooves 97 are pressed andcrushed (compressed amount c) in mutually opposite directions. As aresult, the stiffness of the pair of O-rings 94 is further increased, sothat the radial stiffness and axial damping properties of the bearingsleeve 84 become high. As for the stiffness of the pair of O-rings 94,it is possible to obtain arbitrary stiffness by adjusting the amount ofthe O-rings 94 crushed by adjusting the pressure of the compressed air.In addition, since the pressure acting on both O-rings 94 acts uniformlyon either O-ring 94, their amounts of crushed can be made uniform, sothat the stiffness can be increased while maintaining the balance of thestiffness of both O-rings 94.

EXAMPLE

Next, a description will be given of the results of measurement ofstiffness conducted by using a testing device 110 (its essentialportions are shown in FIG. 16 by way of example).

The testing device 110 is disposed such that a dummy sleeve housing 112with an inside diameter of 85 mm is fitted in a dummy bearing sleeve 111with an outside diameter of 85 mm by providing a fitting gap of 150 μm,the dimensions being identical to those of the actual spindle apparatus80. The two O-ring bearings 96 are provided on the front side bearingside (left-hand side in FIG. 16) of the dummy sleeve housing 112, thetwo o-ring bearings 97 are similarly provided in parallel on the rearside bearing side (right-hand side in FIG. 16) of the dummy bearingsleeve 111. The O-ring 94 with an inside diameter of 84.5 mm and a sizeof 2 mm is installed in each of the O-ring bearings 97 and 96. Inaddition, a pickup of an electric micrometer is attached to an outerperipheral surface 113 of the dummy sleeve housing 112 so as to be ableto detect the amount of radial displacement of the outer peripheralsurface 113 of the dummy sleeve housing 112 (which is also the amount ofdisplacement of the center of the dummy sleeve housing 112) by anelectric micrometer 114.

A load is applied to the testing device 110 thus constructed, bypressing the outer peripheral surface of the dummy sleeve housing 112 inthe direction of arrow B by an air cylinder (not shown).

The respective test conditions other than those described above are asfollows:

Material of the O-ring: A) nitrile rubber B) fluoro rubber Interferenceof the O-ring: A) 0.300 mm B) 0.275 mm C) 0.250 mm Pressure ofcompressed air: A) 0 MPa B) 0.49 MPa Load on two O-rings by the aircylinder: A) 50 N B) 100 NTesting Method Tests are conducted by randomly changing the respectiveconditions including the material of the O-ring, the interference of theO-ring, the pressure of the compressed air, and the load by the aircylinder. The amount of displacement (the amount of displacement of thecenter) of the outer peripheral surface 113 of the dummy sleeve housing112 is measured by the electric micrometer 114. As for the respectivemeasurements, measurements are made five times each, and their averagevalue is set as the result of measurement.(Results of Measurement)

The results of measurement of the stiffness of the O-rings when thepressure of the compressed air is set to 0 MPa (i.e., when there is nosupply of the compressed air) are shown in Table 1 as ratios between theload applied to the dummy sleeve housing 112 by the air cylinder and theamount of displacement of the center. It should be noted that the unitis N/μm, and shows that the greater the numerical value, the greater theradial stiffness.

TABLE 1 Compressed air pressure: 0 MPa Unit: N/μm Material of O-ringnitrile rubber fluoro rubber Interference mm Load N(*) 0.3 0.275 0.250.3 0.275 0.25 100 2.35 1.79 1.47 1.75 1.53 1.33 50 1.93 1.44 1.27 1.561.25 1.10 (*)The load is the one which is applied to the two O-rings.

The results of measurement of the stiffness of the O-rings when thepressure of the compressed air is set to 0.49 MPa are shown in Table 2as ratios between the load applied to the dummy sleeve housing 112 bythe air cylinder and the amount of displacement of the center. It shouldbe noted that the unit is N/μm, and shows that the greater the numericalvalue, the greater the radial stiffness.

TABLE 2 Compressed air pressure: 0.49 MPa Unit: N/μm Material of O-ringnitrile rubber fluoro rubber Interference mm Load N(*) 0.3 0.275 0.250.3 0.275 0.25 100 2.70 2.67 2.30 2.25 2.11 1.94 50 2.27 2.15 1.85 2.051.74 1.51 (*)The load is the one which is applied to the two O-rings.

In addition, the O-rings 94 made of fluoro rubber whose interference isset to 0.250 mm are installed in a random installation order, and theoffset of the center position of the dummy sleeve housing 112 ismeasured five times. The variations (maximum value-minimum value) areshown in Table 3.

TABLE 3 Compressed air pressure MPa 0 0.49 Variation of the amount ofcenter 56 22 displacement μm

As can be appreciated from Table 1, in the case where compressed air isnot supplied to the O-rings 94, the larger the interference of theO-rings 94, the higher the radial stiffness. In addition, the amount ofchange in the radial stiffness with respect to the amount of change ininterference is greater in the case of the fluoro rubber-made O-ringsthan in the case of the nitrile rubber-made O-rings.

From Tables 1 and 2, it can be appreciated that the radial stiffness canbe increased by supplying compressed air to the O-rings 94. This isattributable to the fact that the O-rings 94 are crushed (see FIG. 15)by the compressed air, and the stiffness of the O-rings 94 themselveshas become high. In addition, the smaller the interference, the greaterthe amount of change in the radial stiffness due to the supply ofcompressed air. Furthermore, the amount of change in the radialstiffness due to the supply of the compressed air is greater in the caseof the fluoro rubber-made O-rings than in the case of the nitrilerubber-made O-rings.

As can be appreciated from Table 3, the variation of the amount ofoffset of the center position of the dummy sleeve housing 112 is 56 μmin the case where the compressed air is not supplied, whereas thevariation of the amount of offset is small at 22 μm in the case wherethe compressed air is supplied. Thus, it can be understood that theshapes and attitudes of the O-rings 94 become stabilized by supplyingthe compressed air.

From the above-described test results, it can be understood that bydisposing the plurality of O-rings 94 between the front housing 87 andthe bearing sleeve 84 and by supplying the compressed air between theO-rings 94, it is possible to increase the radial stiffness, and that byadjusting the pressure of the compressed air, it is possible to adjustthe radial stiffness to arbitrary hardness.

It should be noted that the spindle apparatus in accordance with thefifth embodiment is not limited to the above-described modes forcarrying out the invention, and appropriate modifications, improvements,and the like are possible.

For example, in addition to being applied to a machining center, thespindle apparatus may be applied to an NC machine tool, a generalpurpose machine tool for effecting feeding operation manually, and thelike.

In addition, the front and rear side bearings are not limited to angularcontact ball bearings, and may be deep groove ball bearings or rollingbearings such as various roller bearings.

FIGS. 17 and 18 show a sixth embodiment of the invention. Thecharacteristic of this embodiment lies in that a spindle cartridge 133,which includes a rotating shaft 121, front side bearings 122 and 122, afront housing 125, a rotor 127 and a stator 128 of a built-in motor 126,a rear side bearing 130, a rear housing 145, and an outer cylinder 132,is capable of being disassembled and assembled integrally with respectto a spindle head 131.

As shown in FIGS. 17 an 18, a spindle apparatus 120 in accordance withthe sixth embodiment includes the spindle cartridge 133 which includesthe rotatable rotating shaft 121; the front side bearings 122 and 122having inner rings 123 and 123 in which the front end of the rotatingshaft 121 is fitted; the front housing 125 in which outer rings 124 and124 of the front side bearings 122 and 122 are fitted; the rotor 127 ofthe built-in motor 126; the stator 128 of the built-in motor 126; therear side bearing 130 having an inner ring 129 in which the rear end ofthe rotating shaft 121 is fitted; and the outer cylinder 132 fitted inthe spindle head 131. The spindle cartridge 133 is capable of beingdisassembled and assembled integrally with respect to the spindle head131.

Further, the spindle head 131 has a spindle cartridge gripping portion134 in the axial direction, and the spindle cartridge 133 is inserted inthat spindle cartridge gripping portion 134. In addition, the amount ofmovement in a feeding axis direction parallel to the axial direction ofthe rotating shaft 121 is set to be longer than the length necessary forinserting the spindle cartridge 133 into the spindle head 131.

The machine tool 120 is a vertical machining center, and a column isuprightly fixed on a bed 135. A worktable 138, while being supported bya pair of Y-axis guide rails 137 disposed on the bed 135, moves in aY-axis direction which is a feeding axis direction perpendicular to theaxial direction of the rotating shaft 121 in which the worktable 138 isadvanced or retreated with respect to the column 136. A pair of X-axisguide rails 139 are disposed on an upper end of the column 136, and asaddle 140, while being supported by these X-axis guide rails 139, movesin an X-axis direction perpendicular to the axial direction of therotating shaft 121, i.e., in the lateral direction with respect to thecolumns 136 (in a direction perpendicular to the plane of the drawing ofFIG. 17). A pair of Z-axis guide rails 141 are disposed at a leading endof the saddle 140, and the spindle head 131, while being supported bythese Z-axis guide rails 141, moves in such a manner as to advance orretreat with respect to the worktable 138 in a Z direction which is afeeding axis direction parallel to the axial direction of the rotatingshaft 121.

The spindle cartridge 133 includes the rotating shaft 121; the frontside bearings 122; the front housing 125; the rotor 127 for making upthe built-in motor 126; the stator 128 for similarly making up thebuilt-in motor 126; the rear side bearing 130; the rear housing 145; andthe outer cylinder 132. The spindle cartridge 133 is capable of beingdisassembled and assembled integrally with respect to the spindle head131.

The rotating shaft 121 has the rotor 127 in non-contact with the innerperipheral portion of the stator 128. The rotor 127 rotates the rotatingshaft 121 by the rotating magnetic field generated by the stator 128.The rotating shaft 121 is coupled to a tool holder (not shown) throughan interiorly fitted drawbar (not shown).

The outer cylinder 132 is formed in a cylindrical shape, and its one endportion, and the stator 128 is fixed to its inner peripheral surface.The stator 128 generates a rotating magnetic field on its innerperipheral side by an electric current supplied through a motor powersupply cable (not shown).

The front housing 125 is formed in a cylindrical shape and is fixed to afront end of the outer cylinder 132.

The rear housing 145 is formed in a cylindrical shape and is fixed to arear end of the outer cylinder 132. A tool unclamp cylinder 143 of apiston mechanism, in which a rotary joint (not shown) which moves insuch a manner as to advance or retreat to press the drawbar, is joinedto the rear housing 145.

The front side bearings 122 and 122 are multi-row angular contact ballbearings, and the front end portion of the rotating shaft 121 is fittedin the inner rings 123 and 123, respectively, while the outer rings 124and 124 are respectively fitted in the front housing 125.

The rear side bearing 130 is a single-row angular contact ball bearing,and the rear end portion of the rotating shaft 121 is fitted in itsinner ring 129, while its outer ring 144 is fitted in the rear housing145.

According to the machine tool 120 of this embodiment, the amount ofmovement in the feeding axis direction parallel to the axial directionof the rotating shaft 121 is set to be longer than the length necessaryfor inserting the spindle cartridge 133 into the spindle head 131. As aresult, the amount of Z-axis movement, which is the feeding axisdirection parallel to the axial direction of the rotating shaft 121, islonger than the length necessary for inserting the spindle cartridge 133into the spindle head 131. Hence, withdrawal can be performed easily bymaking use of the Z-axis feeding.

FIGS. 19 to 23 show a seventh embodiment of the invention. Acharacteristic of this embodiment lies in that a spindle sub-cartridge151, which a sub-assembly includes the rotating shaft 121, the frontside bearings 122, the front housing 125, the rotor 127 of the built-inmotor 126, the rear side bearing 130, and the bearing sleeve 142, iscapable of being disassembled and assembled integrally with respect tothe spindle head 131. Another characteristic of this embodiment is thatthe amount of movement in the feeding axis direction parallel to theaxial direction of the rotating shaft 121 is set to be longer than thelength necessary for inserting the spindle sub-cartridge 151 into thespindle head 131. Since the other arrangements are identical to those ofthe first embodiment, identical members will be denoted by the samereference numerals, and a detailed description thereof will be omitted.

As shown in FIG. 19, a spindle apparatus 150 in accordance with theseventh embodiment includes the spindle sub-cartridge 151 which is asub-assembly including the rotatable rotating shaft 121; the front sidebearings 122 having the inner rings 123 in which the front end of therotating shaft 121 is fitted; the front housing 125 in which the outerrings 124 of the front side bearings 122 are fitted; the rotor 127 ofthe built-in motor 126; the rear side bearing 130 having the inner ring129 in which the rear end of the rotating shaft 121 is fitted; and thebearing sleeve 142 in which the outer ring 144 of the rear side bearing130 is fitted. The spindle sub-cartridge 151 is capable of beingdisassembled and assembled integrally with respect to the spindle head131. In addition, the amount of movement in the feeding axis directionparallel to the axial direction of the rotating shaft 121 is set to belonger than the length necessary for inserting the spindle sub-cartridge151 into the spindle head 131.

In the case of the machine tool of the vertical machining center, if theamount of Z-axis movement L3 of the spindle head 131, which moves in theZ-axis direction while being supported by the Z-axis guide rails 141,becomes long, the machine height H1 inevitably becomes high. The machineheight H1 is subject to restrictions of the height at the time oftransportation on a road, the height of entrance/exit sections of afactory at the time of the carrying in and out of the machine, and theceiling height of the installation site. For this reason, with themachine tool 150, the length L4 necessary for completely withdrawing thespindle sub-cartridge 151, i.e., the sub-assembly, from the spindle head131 is smaller than the length L1 necessary for withdrawing the spindlecartridge 133 (see FIG. 17), so that the amount of Z-axis movement L3can be made short. Consequently, the machine height H1 can be made low.

As shown in FIG. 20, with the spindle sub-cartridge 151, the outsidediameter φD2 of the bearing sleeve 142 is smaller than the insidediameter φD1 of the stator 128. Further, with the spindle sub-cartridge151, the bearing sleeve 142 is capable of moving freely in the axialdirection downwardly in FIG. 20 with respect to a sleeve housing 152with this bearing sleeve 142 fitted therein. As a result, the spindlesub-cartridge 151, i.e., the sub-assembly, can be integrally withdrawnfrom the outer cylinder 132, with the front housing 125 heading first,by merely removing bolts (not shown) which fasten the spindlesub-cartridge 151 and the outer cylinder 132. At the same time, thespindle sub-cartridge 151 can be disassembled and assembled integrallywith respect to the spindle head 131 without performing the operation ofremoving a cooling oil supplying hose 153, an oil pressure supplyinghose 154, and a motor power cable 155, which are disposed on the sleevehousing 152. It is thereby possible to shorten the replacement time.

Next, referring to FIGS. 21 to 23, a description will be given of theprocedure of dismounting the spindle sub-cartridge 151 in the machinetool 150 in accordance with the seventh embodiment.

As shown in FIG. 21, the spindle head 131 is first lowered to a lowestposition A1 by making use of the Z-axis feeding. The fixation of thefront housing 125 to the outer cylinder 132 is released there.

As shown in FIG. 22, the spindle head 131 is raised to a highestposition A2 by making use of the Z-axis feeding. Since the spindle head131 is raised together with the sleeve housing 152 and the outercylinder 132 having the stator 128, only the spindle sub-cartridge 151,i.e., the sub-assembly, is left, so that this spindle sub-cartridge 151can be removed integrally.

As shown in FIG. 23, the remaining parts, such as the sleeve housing 152and the outer cylinder 132 having the stator 128, can be removed byreleasing the tightening of the spindle head 131 to the outer cylinder132. At this time, in order to integrally remove the remaining parts,such as the sleeve housing 152 and the outer cylinder 132 having thestator 128, the distance L6 from a lower surface of the spindle head 131to an upper surface of the worktable 137 must be longer than the overalllength L5 of the remaining parts. However, since the spindlesub-cartridge 151 is already disassembled, it is readily possible toestablish the relationship of L5<L6. It is thereby possible to shortenthe amount of Z-axis movement L3 and lower the machine height H1.

According to the machine tool 150 of this embodiment, the spindlesub-cartridge 151 includes the rotating shaft 121, the front sidebearings 122, the front housing 125, the rotor 127, the rear sidebearing 130, and the bearing sleeve 142. This spindle sub-cartridge 151is disposed so as to be capable of being disassembled and assembledintegrally with respect to the spindle head 131. Accordingly, thespindle sub-cartridge 151, i.e., the sub-assembly, which requiresinspection, repair, or replacement can be dismounted as a single unitfrom the spindle head 131, and can be disassembled and assembled withoutdisassembling the entire machine tool 150.

FIG. 24 shows an eighth embodiment of the invention. A characteristic ofthis embodiment lies in that the spindle cartridge 133 can bedisassembled integrally and can be assembled integrally as a singleunit. Another characteristic of this embodiment is that a spindle head161 has the spindle cartridge gripping portion 134 for accommodating thespindle cartridge 133, and the spindle cartridge gripping portion 134can be disassembled by being divided at a position for dividing at leastin half. Since the other arrangements are identical to those of thefirst embodiment, identical members will be denoted by the samereference numerals, and a detailed description thereof will be omitted.

As shown in FIG. 24, with a machine tool 160 of the eighth embodiment,the spindle cartridge 133 can be disassembled integrally and can beassembled integrally as a single unit. In addition, the spindle head 161has the spindle cartridge gripping portion 134 for accommodating thespindle cartridge 133. Further, the spindle cartridge gripping portion134 of the spindle head 161 can be disassembled by being divided at aposition for dividing at least in half.

In the machine tool 160, the spindle head 161 has a first spindle headportion 163 and a second spindle head portion 164 which are divided atthe portion of a center line 162 of the rotational axis, the two spindlehead portions 163 and 164 being fastened by bolts 165. Further, thespindle cartridge 133 is fastened to both of the integrated firstspindle head portion 163 and second spindle head portion 164 by bolts167 through a flange portion 166.

With the machine tool 160, when the spindle cartridge 133 is replaced,the spindle cartridge 133 can be dismounted integrally as a single unitirrespective of the length of the Z-axis stroke by removing the firstspindle head portion 163 from the second spindle head portion 164 byremoving the bolts 165, and that operation can be performed easily.Here, the second spindle head portion 164 is set to a mass which can beheld by a person.

It should be noted that the spindle apparatuses in accordance with thesixth, seventh, and eighth embodiments are not limited to theabove-described modes for carrying out the invention, and appropriatemodifications, improvements, and the like are possible.

For example, in addition to being applied to a machining center, thespindle apparatus may be applied to an NC machine tool, a generalpurpose machine tool for effecting feeding operation manually, and thelike.

In addition, the front and rear side bearings are not limited to angularcontact ball bearings, and may be deep groove ball bearings or rollingbearings such as various roller bearings.

FIGS. 25 to 29 show a ninth embodiment of the invention. Thecharacteristics of this embodiment are as follows: There are provided anouter cylinder 181, a spindle head 183, a rotating shaft 184, front sidebearings 186 and 186, a rear side bearing 188, a front housing 191, asleeve housing 193, and a tool unclamp cylinder 194. The rotating shaft184, the front side bearings 186, the rear side bearing 188, the fronthousing 191, and the sleeve housing 193 are integrally assembled to forma spindle sub-cartridge 195 which is a sub-assembly. The spindlesub-cartridge 195, the outer cylinder 181, and the tool unclamp cylinder194 are arranged in a three-divided form. The spindle sub-cartridge 195,which is the sub-assembly, is made withdrawable from the outer cylinder181.

As shown in FIG. 25, a spindle apparatus 180 in accordance with theninth embodiment includes the outer cylinder 181 having a stator 182;the spindle head 183 in which the outer cylinder 181 is fitted; therotatable rotating shaft 184 having a rotor 185 disposed inside thestator 182; the front side bearings 186 and 186 having inner rings 187and 187 in which one end of the rotating shaft 184 is fitted; the rearside bearing 188 having an inner ring 189 in which the other end of therotating shaft 184 is fitted; the front housing 191 in which outer rings190 and 190 of the front side bearings 186 and 186 are fitted and whichis installed on one end of the outer cylinder 181; the sleeve housing193 in which an outer ring 192 of the rear side bearing 188 is fittedand which is fitted in the other end of the outer cylinder 181; and thetool unclamp cylinder 194 fixed to the one end of the outer cylinder181. The rotating shaft 184 with the rotor 185, the front side bearings186, the rear side bearing 188, the front housing 191, and the sleevehousing 193 are integrally assembled to form the spindle sub-cartridge195. That spindle sub-cartridge 195, the outer cylinder 181, and thetool unclamp cylinder 194 are arranged in a three-divided form, and thespindle sub-cartridge 195 is withdrawable from the outer cylinder 181.

In addition, the tool unclamp cylinder 194 is withdrawable from theouter cylinder 181, and an assembly (first assembly) (shown in FIG. 28)196 of the tool unclamp cylinder 194 and the outer cylinder 181 with thespindle sub-cartridge 195 withdrawn therefrom is withdrawable from thespindle head 183.

Meanwhile, an assembly (second assembly) (shown in FIG. 29) 197 of thespindle sub-cartridge 195, the outer cylinder 181, and the tool unclampcylinder 194 is withdrawable from the spindle head 183. A sensor(rotation sensor) 198 for detecting the rotation of the rotating shaft184 is disposed between the rotating shaft 184 and the outer cylinder181.

The outer cylinder 181 is formed in a cylindrical shape, and its one endportion, which is located on the lower side in FIG. 25, is formed as afront housing fixing portion 199. Further, the outer cylinder 181 has asleeve housing fixing portion 200 formed at the other end portion whichis located on the upper side in FIG. 25. An electric cable insertingportion 201 is formed in the sleeve housing fixing portion 200. Thestator 182 is fixed to an inner peripheral surface of the outer cylinder181. The stator 182 generates a rotating magnetic field on its innerperipheral side by an electric current supplied through the power supplywiring 202.

The spindle head 183 detachably grips the outer cylinder 181, and in thecase of a horizontal machining center, for example, the spindle head 183vertically moves along the Y-axis guide rails of a column fixeduprightly on a bed.

The rotating shaft 184 has the rotor 185 in non-contact with the innerperipheral portion of the stator 182. The rotor 185 rotates the rotatingshaft 184 by the rotating magnetic field generated by the stator 182.The rotating shaft 184 is coupled to a tool holder (not shown) throughan interiorly fitted drawbar 203.

The front side bearings 186 and 186 are multi-row angular contact ballbearings, and one end portion of the rotating shaft 184 is fitted in theinner rings 187 and 187, respectively, and the outer rings 190 and 190are respectively fitted in the front housing 191.

The front housing 191 is formed in a cylindrical shape, and an outercylinder interiorly-fitting portion 204 is formed in an end portion ofthe outer cylinder 181. Further, the front housing 191 has an outerperipheral member 205 fitted over its outer peripheral portion. Aplurality of U-grooved fluid channels 206 are formed circumferentiallyin the front housing 191 with respect to this outer peripheral member205. The fluid channels 206 are communicatingly connected to a coolingoil supplying hose 207 installed on the tool unclamp cylinder 194.

The rear side bearing 188 is a single-row angular contact ball bearing,and the other end portion of the rotating shaft 184 is fitted in itsinner ring 189, while its outer ring 192 is fitted in the sleeve housing193.

The sleeve housing 193 is formed in a cylindrical shape and is fitted inthe sleeve housing fixing portion 200 of the outer cylinder 181.

Further, the rotation sensor 198 is disposed at the other end portion ofthe rotating shaft 184. The rotation sensor 198 consists of a rotator208 fixed to the other end portion of the rotating shaft 184 and anelectrical signal generator 209 fixed to the outer cylinder 181 in closeproximity to the outer periphery of this rotator 208. As the rotator 208rotates together with the rotating shaft 184, the electrical signalgenerator 209 electrically converts magnetism imparted from the rotator208 to generate a pulse-like rotation signal, for example. The generatedrotation signal is transferred to and monitored by a controller (notshown) through a sensor signal line (not shown) and a transmitter (notshown).

The tool unclamp cylinder 194 is detachably fixed to one end portion ofthe outer cylinder 181, and has a piston 210 fitted therein for movingin such a manner as to advance and retreat to press the drawbar 203. Inaddition, the power supply wiring 202 is installed on the tool unclampcylinder 194 through a plug 211, and the cooling oil supplying hose 207is screwed down thereto. The cooling oil supplying hose 207 iscommunicatingly connected to the fluid channels 206 through the interiorof this tool unclamp cylinder 194 and the interior of the outer cylinder181.

In such a spindle apparatus 180, the rotating shaft 184 with the rotor185, the front side bearings 186, the rear side bearing 188, the fronthousing 191, the sleeve housing 193, and the rotator 208 of the rotationsensor 198 are integrally assembled to form the spindle sub-cartridge195. The spindle sub-cartridge 195, the outer cylinder 181, and the toolunclamp cylinder 194 are arranged in a three-divided form.

As shown in FIG. 26, in the spindle apparatus 180, all of the outsidediameter D1 of the rotor 185, the outside diameter D2 of the sleevehousing 193, and the outside diameter D3 of the rotator 208 of therotation sensor 198 are set to be smaller than the inside diameter D4 ofthe stator 182. For this reason, the spindle sub-cartridge 195 can bewithdrawn from the outer cylinder 181, with the front housing 191heading first. As a result, when it has become necessary to performmaintenance, such as inspection, repair, and replacement, with respectto the rotating shaft 184 with the rotor 185, the front side bearings186, the rear side bearing 188, the front housing 191, the sleevehousing 193, and the rotator 208 of the rotation sensor 198, which makeup the spindle sub-cartridge 195, it is possible to easily perform themaintenance operation of the spindle sub-cartridge 195.

As shown in FIG. 27, in the spindle apparatus 180, the tool unclampcylinder 194 is detachably fixed to the end portion of the outercylinder 181. For this reason, since only the tool unclamp cylinder 194can be easily withdrawn from the outer cylinder 181, when it has becomenecessary to perform maintenance, such as inspection, repair, andreplacement, with respect to a rotary joint 212, the plug 211 of thepower supply wiring 202, and the cooling oil supplying hose 207, whichare disposed on the tool unclamp cylinder 194, it is possible to easilyperform the maintenance operation for them. Furthermore, by removing thetool unclamp cylinder 194, it is possible to easily perform themaintenance operation, such as inspection, repair, and replacement, inthe electrical signal generator 209 of the rotation sensor 198.

As shown in FIG. 28, with the spindle apparatus 180, since the outercylinder 181 is detachably gripped by the spindle head 183, the firstassembly 196 made up of the tool unclamp cylinder 194 and the outercylinder 181 with the spindle sub-cartridge 195 withdrawn therefrom canbe withdrawn from the spindle head 183. As a result, when it has becomenecessary to perform maintenance, such as inspection, repair, andreplacement, with respect to the outer cylinder 181, it is possible toeasily perform the maintenance operation of the outer cylinder 181.

As shown in FIG. 29, with the spindle apparatus 180, since the outercylinder 181 is detachably gripped by the spindle head 183, the secondassembly 197 made up of the spindle sub-cartridge 195, the outercylinder 181, and the tool unclamp cylinder 194 can be withdrawn fromthe spindle head 183. As a result, when it has become necessary toperform maintenance, such as inspection, repair, and replacement, withrespect to the second assembly 197 made up of the spindle sub-cartridge195, the outer cylinder 181, and the tool unclamp cylinder 194, it ispossible to easily perform the maintenance operation of the secondassembly 197.

According to the spindle apparatus 180 of the ninth embodiment, therotating shaft 184 with the rotor 185, the front side bearings 186, therear side bearing 188, the front housing 191, and the sleeve housing 193are integrally assembled to form the spindle sub-cartridge 195, and thespindle sub-cartridge 195; the outer cylinder 181, and the tool unclampcylinder 194 are arranged in a three-divided form; and the spindlesub-cartridge 195 can be withdrawn from the outer cylinder 181.Accordingly, since the rotating shaft 184 with the rotor 185, the frontside bearings 186, the rear side bearing 188, the front housing 191, andthe sleeve housing 193, which make up the spindle sub-cartridge 195, canbe withdrawn integrally from the outer cylinder 181, only the rotatingshaft 184, the front side bearings 186, and the rear side bearing 188which require inspection, repair, or replacement can be easilydismounted without disassembling the entire spindle apparatus 180.

In addition, according to the spindle apparatus 180 of the ninthembodiment, the tool unclamp cylinder 194 is withdrawable from the outercylinder 181. As a result, only the tool unclamp cylinder 194 whichrequires inspection, repair, or replacement can be easily dismountedwithout disassembling the entire spindle apparatus 180.

In addition, according to the spindle apparatus 180 of the ninthembodiment, the first assembly 196 of the tool unclamp cylinder 194 andthe outer cylinder 181 with the spindle sub-cartridge 195 withdrawntherefrom is withdrawable from the spindle head 183. As a result, inaddition to the spindle sub-cartridge 195, the first assembly 196 of theouter cylinder 181 and the tool unclamp cylinder 194 which requiresinspection, repair, or replacement can be easily dismounted from thespindle head 183 without disassembling the entire spindle apparatus 180.

In addition, according to the spindle apparatus 180 of the ninthembodiment, the second assembly 197 of the spindle sub-cartridge 195,the outer cylinder 181, and the tool unclamp cylinder 194 iswithdrawable from the spindle head 183. As a result, the second assembly197 of the spindle sub-cartridge 195, the outer cylinder 181, and thetool unclamp cylinder 194 which requires inspection, repair, orreplacement can be easily dismounted from the spindle head 183 withoutdisassembling the entire spindle apparatus 180.

FIG. 30 shows a 10th embodiment of the invention. The characteristic ofthis embodiment lies in that a coupler 221 on which various fluidpipings and various power supply cables are disposed is detachablymounted on the tool unclamp cylinder 194. Since the other arrangementsare identical to those of the first embodiment, identical members willbe denoted by the same reference numerals, and a detailed descriptionthereof will be omitted.

As shown in FIG. 30, a spindle apparatus 220 in accordance with the 10thembodiment adopts the spindle cartridge system, the coupler 221 on whichvarious fluid pipings and various power supply cables are disposed isdetachably mounted on the tool unclamp cylinder 194.

Here, oil and air pressure pipings necessary for a spindle cartridge 222include a cooling oil supply line, an oil pressure supply line, acutting fluid supply line, an air purge supply line, a taper cleaningair supply line, and the like. In addition, electric cables necessaryfor the spindle cartridge 222 include a motor power cable, a motorrotation sensor cable, a detection switch cable, and the like. Further,when the spindle cartridge 222 is disassembled from or assembled to thespindle head 183, it is necessary to disengage these many fluid pipingsand the power cables, and the operation takes time. Accordingly, thespindle apparatus 220 uses the coupler 221 in which those portions ofthe various fluid pipings and the various power cables that areconnected to the spindle cartridge 222 are integrated.

In the coupler 221, connected to a plug 225 are the cooling oilsupplying hose 207 for supplying cooling oil to fluid channels 223formed in the outer peripheral portion of the outer cylinder 181 and tothe fluid channels 206 in the front housing 191; an oil pressure hose224 for supplying oil pressure to the tool unclamp cylinder 194; and thepower supply wiring 202. Further, a socket 227 is fixed to a sleevehousing 226 which is coupled to the outer end portion of the outercylinder 181 and in which the outer ring 192 of the rear side bearing188 is fitted. The plug 225 and the socket 227 are fixed by pawls 228,and the pawls 228 are fastened to each other by being merely pressed.When the plug 225 is removed, the plug 225 is adapted to be pulled outby releasing the catches.

In addition, a seal 229 is disposed in the oil and air pressure linesbetween the plug 225 and the socket 227, so that oil and air areprevented from leaking. At this time, if a valve, which is opened andclosed by the attaching and detaching operation, is incorporated in theoil pressure line, no oil leakage occurs when the coupler 221 isremoved, so that the operating efficiency is excellent. In addition, acable coupler 230 is provided for the coupler 221, and the cable coupler230 is attached or detached at the same time as the attaching anddetaching operation of the coupler 221. Such a structure may be appliedto such as the cutting fluid supply line, the air purge supply line, thetaper cleaning air supply line, the motor rotation sensor cable, and thedetection switch cable.

By so doing, when the spindle cartridge 222 is disassembled from orassembled to the spindle head 183, the power supply wiring 202 and themany oil and air pressure pipings, such as the cooling oil supply hose207 and the oil pressure supply hose 224, can be disengaged at one timewithout a tool, making it possible to reduce the operating time. Inaddition, as the power supply coupler 230 and opening and closing valvesfor the various fluid pipings 207 and 224 are provided for the coupler221, if the operation is performed at the time of inspection, repair, orreplacement after closing the various fluid pipings 207 and 224 andremoving the power supply wiring 202, the operation can be performedwhile preventing the leakage of the fluid, entanglement of the powersupply wiring, and the like. At this time, fastening with two or threebolts, for example, may be used instead of the coupler 221. By so doing,the structure can be made simple without greatly losing the operatingefficiency. Further, if the structure having such a coupler 221 isapplied to the spindle sub-cartridge system, when the front side bearing186 or the rear side bearing 188 is replaced, the replacement time canbe shortened by removing the spindle sub-cartridge 195 (see FIG. 25),and when the stator 182 is replaced, the entire spindle cartridge can bereplaced in a short time by removing the coupler 221.

It should be noted that the spindle apparatuses in accordance with theninth and 10th embodiments are not limited to the above-described modesfor carrying out the invention, and appropriate modifications,improvements, and the like are possible.

For example, in addition to being applied to a machining center, thespindle apparatus may be applied to an NC machine tool, a generalpurpose machine tool for effecting feeding operation manually, and thelike.

In addition, the front and rear side bearings are not limited to angularcontact ball bearings, and may be deep groove ball bearings or rollingbearings such as various roller bearings.

Although the invention is described in detail and with reference tospecific embodiments, it will be obvious to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention.

This application is based on Japanese Patent Application filed on Apr.7, 2003 (Japanese Patent Application No. 2003-103219), Japanese PatentApplication filed on Dec. 17, 2003 (Japanese Patent Application No.2003-419854), Japanese Patent Application filed on Mar. 31, 2003(Japanese Patent Application No. 2003-096503), Japanese PatentApplication filed on Jan. 5, 2004 (Japanese Patent Application No.2004-000261), and Japanese Patent Application filed on Nov. 14, 2003(Japanese Patent Application No. 2003-384703), the contents of which areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

As described above, the spindle apparatus and the machine tool havingthe spindle apparatus in accordance with the invention make it possibleto provide a spindle apparatus which facilitates assembling and removingoperations at the time of maintenance and which is low cost. Further,the spindle apparatus and the machine tool having the spindle apparatusin accordance with the invention make it possible to provide a spindleapparatus which has high stiffness and excels in satisfactory dampingproperties and slidability. Still further, the spindle apparatus and themachine tool having the spindle apparatus in accordance with theinvention make it possible to provide a machine tool in which a spindlecartridge or a spindle sub-cartridge can be disassembled and assembledin a short time, which minimizes the machine height, and which has highstiffness. Furthermore, the spindle apparatus and the machine toolhaving the spindle apparatus in accordance with the invention make itpossible to attain improvement of the maintenance efficiency by makingit possible to facilitate the operation of replacing all internalcomponent parts.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, a sub-assembly made up of the fronthousing, the rotating shaft, and the bearing sleeve is withdrawable fromthe outer cylinder. As a result, the assembling efficiency improves, andthese parts can be replaced speedily when they became damaged. Inaddition, as for the bearing sleeve, since the rear side bearing is inan assembled state, the state of grease does not change in thewithdrawal and insertion of the sub-assembly.

Accordingly, with this spindle apparatus, as the sub-assembly is kept instock after performing the running-in operation in advance by usinganother outer cylinder, the sub-assembly can be replaced at the time ofthe damage of the spindle apparatus, and the normal operation is madepossible immediately, thereby permitting a substantial reduction indowntime. In addition, a cost reduction is made possible in comparisonwith the replacement of the entire spindle apparatus, and a reduction ininventory cost is also made possible. As a result, it becomes possibleto overcome the conventional problem that the downtime becomes longsince the running-in operation of the bearings is required afterassembly in the case of grease lubrication for which the time andtrouble in maintenance cannot be reduced.

In addition, the diameter becomes smaller in the order of the innerperipheral diameter of the outer cylinder, the inside diameter of thestator, and the outside diameter of the bearing sleeve. To ensure thatthe non-rotating part does not constitute a hindrance when an attempt ismade to withdraw the spindle in the rear of the bearing sleeve, theradius of the rotating part in an arbitrary section is smaller than aminimum radius of the non-rotating part between the rear end of thebearing sleeve and that section, thereby preventing the non-rotatingpart from constituting a hindrance. Accordingly, when an attempt is madeto withdraw the sub-assembly, the piston mechanism and the like, whichare the non-rotating part, for holding/releasing the tool do notconstitute a hindrance

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the sub-assembly made up of the fronthousing, the rotating shaft, and the bearing sleeve is withdrawable fromthe outer cylinder. As a result, the assembling efficiency improves, andthese parts can be replaced speedily when they became damaged. Inaddition, as for the bearing sleeve, since the rear side bearing is inan assembled state, the state of grease does not change in thewithdrawal and insertion of the sub-assembly.

Accordingly, with this spindle apparatus, as the sub-assembly is kept instock after performing the running-in operation in advance by usinganother outer cylinder, the sub-assembly can be replaced at the time ofthe damage of the spindle apparatus, and the normal operation is madepossible immediately, thereby permitting a substantial reduction indowntime. In addition, a cost reduction is made possible in comparisonwith the replacement of the entire spindle apparatus, and a reduction ininventory cost is also made possible.

In addition, since the tool replacement is effected through the pistonmechanism by the inside diameter part incorporated in the rotatingshaft, in comparison with an externally exposed type, it is possible toeffect the tool replacement with high lubricating performance.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, unclamping can be performedappropriately as the distance between the mounting reference plane ofthe sub-assembly and the piston pressing surface of the inside diameterpart is adjusted to within ±0.1 mm relative to the reference dimension.Therefore, piston adjustment is made unnecessary at the time ofperforming the replacement of the sub-assembly, making it possible toimprove the maintenance efficiency.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the inside diameter part isincorporated in such a manner as to be capable of compressing a spring,and the adjustment part is fixed to a rear portion of the insidediameter part, the piston pressing surface for pressing the pistonmechanism being formed on the adjustment part. Therefore, since theamount of pushing of the tool holder can be set to a predetermined valueby the adjustment part, it is possible to appropriately effectunclamping by adjusting its tolerance. As a result, piston adjustment ismade unnecessary at the time of performing replacement of the insidediameter part, making it possible to improve the maintenance efficiency.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the front housing is fitted to theouter cylinder with an interference fit. Therefore, in cases such aswhere the sub-assembly is subjected to disassembly, assembly, orreplacement, offset does not occur between the axes of the front housingand the outer cylinder, making it possible to maintain high accuracy.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the bearing sleeve is fitted in thesleeve housing, and the outside diameter of the bearing sleeve isclearance-fitted with respect to the inside diameter of the sleevehousing. Therefore, the rear side bearing and the bearing sleevefunction mainly to support the rotating shaft, but are capable ofabsorbing with a simple structure the axial displacement such as thermalexpansion due to the heat generation by the rotor.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, a plurality of pairs of O-rings areinterposed between the outside diameter of the bearing sleeve and theinside diameter of the sleeve housing. Therefore, the leakage of thelubricant is prevented by the plurality of pairs of O-rings between theoutside diameter of the bearing sleeve and the inside diameter of thesleeve housing, and the vibration of the bearing sleeve can be damped bythe damping effect based on the interference of the O-rings.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the ratio between, on the one hand, afitting length of the bearing sleeve and the sleeve housing and, on theother hand, the outside diameter of the bearing sleeve is set within arange of “fitting length/outside diameter=0.45 to 0.8.” Therefore, theoutside diameter of the bearing sleeve and the length of the fittingportion of the sleeve housing are set to an appropriate relationship, sothat it is possible to obtain a structure of the sub-assembly excellingin the maintenance efficiency and the performance of the machine tool.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, there are provided a plurality oflubricant discharging holes provided circumferentially in the bearingsleeve, circumferential grooves provided in a fitting surface of theouter periphery of the bearing sleeve, and radial lubricant supplyingpassages communicatingly connected to the circumferential grooves.Therefore, it becomes possible to discharge the lubricant without aproblem at whatever phase the bearing sleeve may be. Although adischarging hole is required on the lower side in the case of, forinstance, a horizontally mounted spindle, discharging can be effectedsince one of the holes faces the lower side. Furthermore, the lubricantcan be supplied at whatever position the bearing sleeve may be.Accordingly, it becomes unnecessary to adjust the phase of the bearingsleeve, so that the operating efficiency in maintenance is excellent.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the rear side bearing is a back-to-backarrangement angular contact ball bearing with fixed-position preload.Therefore, it is possible to absorb with a simple structure the axialdisplacement such as thermal expansion due to the heat generation by therotor.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, grease lubrication is adopted.Therefore, maintenance can be performed at a small cost by virtue ofgrease lubrication which is easy to handle and is relativelyinexpensive.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, a grease replenishing unit is provided.Therefore, it is possible to replenish the shortage of grease by thegrease replenishing unit, making it possible to avoid a seizure and thelike.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, a mechanism is provided for dischargingexcess grease after the supply of grease. Therefore, the lubricant whichis supplied to the interior of the bearing and has become unnecessaryadheres to a rotating member such as an outer ring spacer disposed inthe vicinity of the bearing. The lubricant adhering to the rotatingmember is slung off to outside the bearing by the rotational force.Consequently, the lubricant which became unnecessary can be forciblydischarged to outside the bearing.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, a very small amount of lubrication ofany one of oil-air, oil-mist, and direct-injection lubrication is used.Therefore, it is possible to effect highly efficient lubrication througha very small amount of lubrication of any one of oil-air, oil-mist, anddirect-injection lubrication, so that anti-seizure properties can beimproved further.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, an elastic body is arranged betweenfitting surfaces of the sleeve housing and the bearing sleeve mademovable in the axial direction of the rotating shaft by fitting to thesleeve housing. Therefore, it is possible to increase the radialstiffness by the elastic body and improve the damping factor on theaxial direction, thereby making it possible to prevent the self-excitedvibration of the rotating shaft. In addition, since a fluid for applyingpressure is arranged to be supplied to the elastic body, it is possibleto further increase the radial stiffness by allowing the elastic body tobe deformed, and enhance the effect of suppressing the self-excitedvibration of the rotating shaft by improving the damping factor on theaxial direction.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the elastic body is an O-ring, and thefluid is compressed air, the compressed air being supplied between theO-rings provided in a plural number, so as to apply the pressure to theO-rings. Therefore it is possible to effectively prevent theself-excited vibration of the rotating shaft by increasing the radialstiffness while maintaining high slidability. In addition, since theO-ring excels in workability and versatility, a high-performance spindleapparatus can be fabricated without requiring a complex manufacturingprocess.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the pressure of the fluid for applyingpressure to the elastic body is made variable. Therefore, the amount ofdeformation of the elastic body due to the pressure of the fluid can bevaried by changing the pressure in correspondence with the workingconditions of the spindle apparatus. In addition, the self-excitedvibration of the rotating shaft can be effectively prevented by settingthe radial stiffness and the damping factor of the elastic body tovalues optimal to the working conditions. In addition, the radialstiffness and the damping factor of the elastic body can be changed bymerely changing the pressure of the fluid supplied, and can be changedvery easily.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the O-ring is formed of nitrile rubberor fluoro rubber, and the interference of the O-ring is set to be notless than 10% of a working standard value and not more than the workingstandard value. Therefore, the O-ring has a sealing effect and anelastically supporting effect, has wear resistance against the axialmovement and heat resistance against heat generation, and can thereby bemade to have a long life. In addition, it is possible to improve theradial stiffness and the axial damping properties while maintaining theslidability by appropriately increasing the stiffness of the O-ring.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, a plurality of sets of elastic bodiesare disposed, each of the sets being formed by a plurality of elasticbodies, one of the sets of elastic bodies arranged at both ends beingdisposed on the bearing sleeve, the other one of the sets of elasticbodies on the sleeve housing. Consequently, the assembly is facilitated,and the possibility of causing damage to the O-rings is small. It shouldbe noted that the effect whereby the movement of the bearing sleeve isallowed to take place uniformly an stably in cases where various loadsare applied to the spindle apparatus is identical to a case where theelastic body is disposed only on the bearing sleeve and a case where itis disposed only on the sleeve housing. Further, an arrangement may beprovided such that two elastic bodies are disposed in the spindleapparatus, one on the bearing sleeve and the other on the sleevehousing, and a fluid is supplied to between the elastic bodies.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the spindle cartridge is inserted inthe spindle cartridge gripping portion provided in the axial directionof the spindle head, and the amount of movement in the feeding axisdirection parallel to the axial direction of the rotating shaft is setto be longer than the length necessary for inserting the spindlecartridge into the spindle head. The spindle cartridge is therebycapable of being disassembled and assemble integrally with respect tothe spindle head. Consequently, since the amount of movement in thez-axis, which is the feeding axis direction parallel to the axialdirection of the rotating shaft, is set to be longer than the lengthnecessary for inserting the spindle cartridge into the spindle head, itis possible to easily effect the withdrawal making use of the z-axisfeeding.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the amount of movement in the feedingaxis direction parallel to the axial direction of the rotating shaft isset to be longer than the length necessary for inserting the spindlesub-cartridge into the spindle head. The spindle sub-cartridge isthereby capable of being disassembled integrally with respect to thespindle head. Consequently, since the amount of movement in the z-axisdirection, which is the feeding axis direction parallel to the axialdirection of the rotating shaft, is set to be longer than the lengthnecessary for inserting the spindle sub-cartridge into the spindle head,it is possible to easily effect the withdrawal making use of the z-axisfeeding.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the spindle cartridge gripping portionof the spindle head can be disassembled by being divided at a positionfor dividing at least in half. Consequently, even if, for instance, theamount of Z-axis movement is set to be short, removal and assembly canbe performed by dividing and developing the spindle cartridge grippingportion of the spindle head. Further, the stiffness of the entiremachine tool can be increased by increasing the fastening stiffness ofthe spindle cartridge and the spindle head.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the rotating shaft with the rotor, thefront side bearing, the rear side bearing, the front housing, and thesleeve housing are integrally assembled to form the spindlesub-cartridge, the spindle sub-cartridge, the outer cylinder, and thetool unclamp cylinder are arranged in a three-divided form, and thespindle sub-cartridge is withdrawable from the outer cylinder.

Accordingly, since the rotating shaft with the rotor, the front sidebearing, the rear side bearing, the front housing, and the sleevehousing, which make up the spindle sub-cartridge, can be withdrawnintegrally from the outer cylinder, only the rotating shaft, the frontside bearing, and the rear side bearing which require inspection,repair, or replacement can be easily dismounted without disassemblingthe entire spindle apparatus. Consequently, it becomes possible tocontrol any parts making up the spindle cartridge without removing thewirings and pipings.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, the tool unclamp cylinder iswithdrawable from the outer cylinder. Consequently, since only the toolunclamp cylinder can be easily dismounted without disassembling theentire spindle apparatus, inspection, repair, or replacement is easilypossible for any parts making up the tool unclamp cylinder.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, an assembly of the tool unclampcylinder and the outer cylinder with the spindle sub-cartridge withdrawntherefrom is withdrawable from the spindle head. Consequently, inaddition to the spindle sub-cartridge, an assembly of the outer cylinderand the tool unclamp cylinder can be easily dismounted from the spindlehead without disassembling the entire spindle apparatus, so thatinspection, repair, or replacement is easily possible for any partsmaking up the outer cylinder or the tool unclamp cylinder.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, an assembly of the spindlesub-cartridge, the outer cylinder, and the tool unclamp cylinder iswithdrawable from the spindle head. Consequently, an assembly of thespindle sub-cartridge, the outer cylinder, and the tool unclamp cylindercan be easily dismounted from the spindle head without disassembling theentire spindle apparatus, so that inspection, repair, or replacement iseasily possible for any parts making up the spindle apparatus.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, a coupler having various fluid pipingsand a power supply coupler is detachably installed on the tool unclampcylinder or the outer cylinder. Consequently, as a power supply couplerand opening and closing valves for the various fluid pipings areprovided for the coupler, if the operation is performed at the time ofinspection, repair, or replacement after closing the various fluidpipings and removing the power supply wiring, the operation can beperformed while preventing the leakage of the fluid, entanglement of thepower supply wiring, and the like.

Furthermore, since the spindle apparatus of the invention is constructedand operates as described above, a sensor for detecting the rotation ofthe rotating shaft is disposed between the rotating shaft and the outercylinder. Consequently, the inspection, repair, or replacement of thesensor becomes possible by merely removing the tool unclamp cylinder.

1. A machine tool comprising: a bed; a work table disposed on the bed soas to move in a horizontal direction; a column disposed on the bed toextend upward from the bed in a vertical direction; a spindle headsupported on the column so as to move in the vertical direction withrespect to the work table; an outer cylinder attached inside the spindlehead; a stator of a built-in motor, the stator attached inside the outercylinder; and a spindle sub-cartridge; a tool unclamp cylinder of apiston mechanism; and a sleeve housing in which the bearing sleeve isfitted such that the bearing sleeve is movable with respect to thesleeve housing in the vertical direction; wherein the spindlesub-cartridge comprises: a rotatable rotating shaft, extending in thevertical direction; a front side bearing having an inner ring fittedover one end of the rotating shaft; a front housing in which an outerring of the front side bearing is fitted; a rotor of the built-in motor;a rear side bearing having an inner ring in which a rear end of therotating shaft is fitted; and a bearing sleeve in which an outer ring ofthe rear side bearing is fitted; wherein a movable range of the spindlehead in the vertical direction is longer than a length necessary forinserting the spindle sub-cartridge into the spindle head, wherein thespindle sub-cartridge is adapted to be disassembled and assembledintegrally with respect to the spindle head, and wherein the outercylinder, the stator, the tool unclamp cylinder, and the sleeve housingare adapted to be disassembled and assembled integrally with respect tothe spindle head and separately from the spindle sub-cartridge.